diff --git a/application/basilisk/base/content/browser-syncui.js b/application/basilisk/base/content/browser-syncui.js
index 67056e221..d4f360b77 100644
--- a/application/basilisk/base/content/browser-syncui.js
+++ b/application/basilisk/base/content/browser-syncui.js
@@ -83,10 +83,7 @@ var gSyncUI = {
   _wasDelayed: false,
 
   _needsSetup: function SUI__needsSetup() {
-    let firstSync = "";
-    try {
-      firstSync = Services.prefs.getCharPref("services.sync.firstSync");
-    } catch (e) { }
+    let firstSync = Services.prefs.getCharPref("services.sync.firstSync", "");
     return Weave.Status.checkSetup() == Weave.CLIENT_NOT_CONFIGURED ||
            firstSync == "notReady";
   },
diff --git a/application/basilisk/base/content/browser.js b/application/basilisk/base/content/browser.js
index 009115eba..182f2e188 100644
--- a/application/basilisk/base/content/browser.js
+++ b/application/basilisk/base/content/browser.js
@@ -2586,15 +2586,9 @@ var gMenuButtonUpdateBadge = {
   cancelObserverRegistered: false,
 
   init: function () {
-    try {
-      this.enabled = Services.prefs.getBoolPref("app.update.badge");
-    } catch (e) {}
+    this.enabled = Services.prefs.getBoolPref("app.update.badge", false);
     if (this.enabled) {
-      try {
-        this.badgeWaitTime = Services.prefs.getIntPref("app.update.badgeWaitTime");
-      } catch (e) {
-        this.badgeWaitTime = 345600; // 4 days
-      }
+      this.badgeWaitTime = Services.prefs.getIntPref("app.update.badgeWaitTime", 345600); // 4 days
       Services.obs.addObserver(this, "update-staged", false);
       Services.obs.addObserver(this, "update-downloaded", false);
     }
diff --git a/application/basilisk/base/content/tabbrowser.xml b/application/basilisk/base/content/tabbrowser.xml
index e90391286..b6c6591f1 100644
--- a/application/basilisk/base/content/tabbrowser.xml
+++ b/application/basilisk/base/content/tabbrowser.xml
@@ -4135,11 +4135,7 @@
                 return true;
               if (this._logInit)
                 return this._shouldLog;
-              let result = false;
-              try {
-                result = Services.prefs.getBoolPref("browser.tabs.remote.logSwitchTiming");
-              } catch (ex) {
-              }
+              let result = Services.prefs.getBoolPref("browser.tabs.remote.logSwitchTiming", false);
               this._shouldLog = result;
               this._logInit = true;
               return this._shouldLog;
@@ -5208,11 +5204,7 @@
           window.addEventListener("resize", this, false);
           window.addEventListener("load", this, false);
 
-          try {
-            this._tabAnimationLoggingEnabled = Services.prefs.getBoolPref("browser.tabs.animationLogging.enabled");
-          } catch (ex) {
-            this._tabAnimationLoggingEnabled = false;
-          }
+          this._tabAnimationLoggingEnabled = Services.prefs.getBoolPref("browser.tabs.animationLogging.enabled", false);
           this._browserNewtabpageEnabled = Services.prefs.getBoolPref("browser.newtabpage.enabled");
         ]]>
       </constructor>
diff --git a/application/basilisk/components/customizableui/CustomizableUI.jsm b/application/basilisk/components/customizableui/CustomizableUI.jsm
index 31126b37c..d56d63d99 100644
--- a/application/basilisk/components/customizableui/CustomizableUI.jsm
+++ b/application/basilisk/components/customizableui/CustomizableUI.jsm
@@ -158,10 +158,7 @@ var gUIStateBeforeReset = {
 XPCOMUtils.defineLazyGetter(this, "log", () => {
   let scope = {};
   Cu.import("resource://gre/modules/Console.jsm", scope);
-  let debug;
-  try {
-    debug = Services.prefs.getBoolPref(kPrefCustomizationDebug);
-  } catch (ex) {}
+  let  debug = Services.prefs.getBoolPref(kPrefCustomizationDebug, false);
   let consoleOptions = {
     maxLogLevel: debug ? "all" : "log",
     prefix: "CustomizableUI",
@@ -1914,16 +1911,10 @@ var CustomizableUIInternal = {
   // state immediately when a browser window opens, which is important for
   // other consumers of this API.
   loadSavedState: function() {
-    let state = null;
-    try {
-      state = Services.prefs.getCharPref(kPrefCustomizationState);
-    } catch (e) {
-      log.debug("No saved state found");
-      // This will fail if nothing has been customized, so silently fall back to
-      // the defaults.
-    }
-
+    let state = Services.prefs.getCharPref(kPrefCustomizationState, "");
     if (!state) {
+      log.debug("No saved state found");
+      // Nothing has been customized, so silently fall back to the defaults.
       return;
     }
     try {
@@ -2208,10 +2199,7 @@ var CustomizableUIInternal = {
         this.notifyListeners("onWidgetAdded", widget.id, widget.currentArea,
                              widget.currentPosition);
       } else if (widgetMightNeedAutoAdding) {
-        let autoAdd = true;
-        try {
-          autoAdd = Services.prefs.getBoolPref(kPrefCustomizationAutoAdd);
-        } catch (e) {}
+        let autoAdd = Services.prefs.getBoolPref(kPrefCustomizationAutoAdd, true);
 
         // If the widget doesn't have an existing placement, and it hasn't been
         // seen before, then add it to its default area so it can be used.
diff --git a/application/basilisk/components/customizableui/CustomizableWidgets.jsm b/application/basilisk/components/customizableui/CustomizableWidgets.jsm
index 9e8f0ec78..d4a191a97 100644
--- a/application/basilisk/components/customizableui/CustomizableWidgets.jsm
+++ b/application/basilisk/components/customizableui/CustomizableWidgets.jsm
@@ -40,10 +40,7 @@ const kWidePanelItemClass = "panel-wide-item";
 XPCOMUtils.defineLazyGetter(this, "log", () => {
   let scope = {};
   Cu.import("resource://gre/modules/Console.jsm", scope);
-  let debug;
-  try {
-    debug = Services.prefs.getBoolPref(kPrefCustomizationDebug);
-  } catch (ex) {}
+  let debug = Services.prefs.getBoolPref(kPrefCustomizationDebug, false);
   let consoleOptions = {
     maxLogLevel: debug ? "all" : "log",
     prefix: "CustomizableWidgets",
diff --git a/application/basilisk/components/customizableui/CustomizeMode.jsm b/application/basilisk/components/customizableui/CustomizeMode.jsm
index 4365ddfbc..2958655d2 100644
--- a/application/basilisk/components/customizableui/CustomizeMode.jsm
+++ b/application/basilisk/components/customizableui/CustomizeMode.jsm
@@ -40,9 +40,7 @@ let gDebug;
 XPCOMUtils.defineLazyGetter(this, "log", () => {
   let scope = {};
   Cu.import("resource://gre/modules/Console.jsm", scope);
-  try {
-    gDebug = Services.prefs.getBoolPref(kPrefCustomizationDebug);
-  } catch (ex) {}
+  gDebug = Services.prefs.getBoolPref(kPrefCustomizationDebug, false);
   let consoleOptions = {
     maxLogLevel: gDebug ? "all" : "log",
     prefix: "CustomizeMode",
@@ -1503,10 +1501,7 @@ CustomizeMode.prototype = {
     if (!AppConstants.CAN_DRAW_IN_TITLEBAR) {
       return;
     }
-    let drawInTitlebar = true;
-    try {
-      drawInTitlebar = Services.prefs.getBoolPref(kDrawInTitlebarPref);
-    } catch (ex) { }
+    let drawInTitlebar = Services.prefs.getBoolPref(kDrawInTitlebarPref, true);
     let button = this.document.getElementById("customization-titlebar-visibility-button");
     // Drawing in the titlebar means 'hiding' the titlebar:
     if (drawInTitlebar) {
diff --git a/application/basilisk/components/distribution.js b/application/basilisk/components/distribution.js
index 589129a5a..c30e4dcfe 100644
--- a/application/basilisk/components/distribution.js
+++ b/application/basilisk/components/distribution.js
@@ -22,10 +22,7 @@ XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
 this.DistributionCustomizer = function DistributionCustomizer() {
   // For parallel xpcshell testing purposes allow loading the distribution.ini
   // file from the profile folder through an hidden pref.
-  let loadFromProfile = false;
-  try {
-    loadFromProfile = Services.prefs.getBoolPref("distribution.testing.loadFromProfile");
-  } catch (ex) {}
+  loadFromProfile = Services.prefs.getBoolPref("distribution.testing.loadFromProfile", false);
   let dirSvc = Cc["@mozilla.org/file/directory_service;1"].
                getService(Ci.nsIProperties);
   try {
@@ -60,13 +57,7 @@ DistributionCustomizer.prototype = {
   },
 
   get _locale() {
-    let locale;
-    try {
-      locale = this._prefs.getCharPref("general.useragent.locale");
-    }
-    catch (e) {
-      locale = "en-US";
-    }
+    let locale = this._prefs.getCharPref("general.useragent.locale", "en-US");
     this.__defineGetter__("_locale", () => locale);
     return this._locale;
   },
@@ -291,11 +282,7 @@ DistributionCustomizer.prototype = {
         this._ini.getString("Global", "id") + ".bookmarksProcessed";
     }
 
-    let bmProcessed = false;
-    try {
-      bmProcessed = this._prefs.getBoolPref(bmProcessedPref);
-    }
-    catch (e) {}
+    let bmProcessed = this._prefs.getBoolPref(bmProcessedPref, false);
 
     if (!bmProcessed) {
       if (sections["BookmarksMenu"])
diff --git a/application/basilisk/components/feeds/FeedWriter.js b/application/basilisk/components/feeds/FeedWriter.js
index 20f1399b0..ceb2a7e2f 100644
--- a/application/basilisk/components/feeds/FeedWriter.js
+++ b/application/basilisk/components/feeds/FeedWriter.js
@@ -19,12 +19,7 @@ function LOG(str) {
   let prefB = Cc["@mozilla.org/preferences-service;1"].
               getService(Ci.nsIPrefBranch);
 
-  let shouldLog = false;
-  try {
-    shouldLog = prefB.getBoolPref("feeds.log");
-  }
-  catch (ex) {
-  }
+  let shouldLog = prefB.getBoolPref("feeds.log", false);
 
   if (shouldLog)
     dump("*** Feeds: " + str + "\n");
diff --git a/application/basilisk/components/feeds/WebContentConverter.js b/application/basilisk/components/feeds/WebContentConverter.js
index 2cb5cd145..159eca7c2 100644
--- a/application/basilisk/components/feeds/WebContentConverter.js
+++ b/application/basilisk/components/feeds/WebContentConverter.js
@@ -187,13 +187,8 @@ const Utils = {
 
     // check if it is in the black list
     let pb = Services.prefs;
-    let allowed;
-    try {
-      allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "." + aProtocol);
-    }
-    catch (e) {
-      allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "-default");
-    }
+    let allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "." + aProtocol,
+      pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "-default"));
     if (!allowed) {
       throw this.getSecurityError(
         `Not allowed to register a protocol handler for ${aProtocol}`,
diff --git a/application/basilisk/components/nsBrowserContentHandler.js b/application/basilisk/components/nsBrowserContentHandler.js
index 74144fc1b..d65e52594 100644
--- a/application/basilisk/components/nsBrowserContentHandler.js
+++ b/application/basilisk/components/nsBrowserContentHandler.js
@@ -100,20 +100,14 @@ const OVERRIDE_NEW_BUILD_ID = 3;
  *  OVERRIDE_NONE otherwise.
  */
 function needHomepageOverride(prefb) {
-  var savedmstone = null;
-  try {
-    savedmstone = prefb.getCharPref("browser.startup.homepage_override.mstone");
-  } catch (e) {}
+  var savedmstone = prefb.getCharPref("browser.startup.homepage_override.mstone", "");
 
   if (savedmstone == "ignore")
     return OVERRIDE_NONE;
 
   var mstone = Services.appinfo.platformVersion;
 
-  var savedBuildID = null;
-  try {
-    savedBuildID = prefb.getCharPref("browser.startup.homepage_override.buildID");
-  } catch (e) {}
+  var savedBuildID = prefb.getCharPref("browser.startup.homepage_override.buildID", "");
 
   var buildID = Services.appinfo.platformBuildID;
 
@@ -489,10 +483,7 @@ nsBrowserContentHandler.prototype = {
       // URL if we do end up showing an overridePage. This makes it possible
       // to have the overridePage's content vary depending on the version we're
       // upgrading from.
-      let old_mstone = "unknown";
-      try {
-        old_mstone = Services.prefs.getCharPref("browser.startup.homepage_override.mstone");
-      } catch (ex) {}
+      let old_mstone = Services.prefs.getCharPref("browser.startup.homepage_override.mstone", "unknown");
       override = needHomepageOverride(prefb);
       if (override != OVERRIDE_NONE) {
         switch (override) {
diff --git a/application/basilisk/components/nsBrowserGlue.js b/application/basilisk/components/nsBrowserGlue.js
index e38002de1..47b2a5801 100644
--- a/application/basilisk/components/nsBrowserGlue.js
+++ b/application/basilisk/components/nsBrowserGlue.js
@@ -959,10 +959,7 @@ BrowserGlue.prototype = {
     // Offer to reset a user's profile if it hasn't been used for 60 days.
     const OFFER_PROFILE_RESET_INTERVAL_MS = 60 * 24 * 60 * 60 * 1000;
     let lastUse = Services.appinfo.replacedLockTime;
-    let disableResetPrompt = false;
-    try {
-      disableResetPrompt = Services.prefs.getBoolPref("browser.disableResetPrompt");
-    } catch (e) {}
+    let disableResetPrompt = Services.prefs.getBoolPref("browser.disableResetPrompt", false);
 
     if (!disableResetPrompt && lastUse &&
         Date.now() - lastUse >= OFFER_PROFILE_RESET_INTERVAL_MS) {
@@ -1504,10 +1501,7 @@ BrowserGlue.prototype = {
     } catch (ex) {}
 
     // Support legacy bookmarks.html format for apps that depend on that format.
-    let autoExportHTML = false;
-    try {
-      autoExportHTML = Services.prefs.getBoolPref("browser.bookmarks.autoExportHTML");
-    } catch (ex) {} // Do not export.
+    let autoExportHTML = Services.prefs.getBoolPref("browser.bookmarks.autoExportHTML", false);  // Do not export.
     if (autoExportHTML) {
       // Sqlite.jsm and Places shutdown happen at profile-before-change, thus,
       // to be on the safe side, this should run earlier.
@@ -1577,10 +1571,7 @@ BrowserGlue.prototype = {
         // An import operation is about to run.
         // Don't try to recreate smart bookmarks if autoExportHTML is true or
         // smart bookmarks are disabled.
-        let smartBookmarksVersion = 0;
-        try {
-          smartBookmarksVersion = Services.prefs.getIntPref("browser.places.smartBookmarksVersion");
-        } catch (ex) {}
+        let smartBookmarksVersion = Services.prefs.getIntPref("browser.places.smartBookmarksVersion", 0);
         if (!autoExportHTML && smartBookmarksVersion != -1)
           Services.prefs.setIntPref("browser.places.smartBookmarksVersion", 0);
 
@@ -1931,10 +1922,7 @@ BrowserGlue.prototype = {
       // Refactor urlbar suggestion preferences to make it extendable and
       // allow new suggestion types (e.g: search suggestions).
       let types = ["history", "bookmark", "openpage"];
-      let defaultBehavior = 0;
-      try {
-        defaultBehavior = Services.prefs.getIntPref("browser.urlbar.default.behavior");
-      } catch (ex) {}
+      let defaultBehavior = Services.prefs.getIntPref("browser.urlbar.default.behavior", 0);
       try {
         let autocompleteEnabled = Services.prefs.getBoolPref("browser.urlbar.autocomplete.enabled");
         if (!autocompleteEnabled) {
@@ -1987,12 +1975,8 @@ BrowserGlue.prototype = {
 
     if (currentUIVersion < 30) {
       // Convert old devedition theme pref to lightweight theme storage
-      let lightweightThemeSelected = false;
-      let selectedThemeID = null;
-      try {
-        lightweightThemeSelected = Services.prefs.prefHasUserValue("lightweightThemes.selectedThemeID");
-        selectedThemeID = Services.prefs.getCharPref("lightweightThemes.selectedThemeID");
-      } catch (e) {}
+      let lightweightThemeSelected = Services.prefs.prefHasUserValue("lightweightThemes.selectedThemeID", false);
+      let selectedThemeID = Services.prefs.getCharPref("lightweightThemes.selectedThemeID", "");
 
       let defaultThemeSelected = false;
       try {
@@ -2142,10 +2126,7 @@ BrowserGlue.prototype = {
     const MAX_RESULTS = 10;
 
     // Get current smart bookmarks version.  If not set, create them.
-    let smartBookmarksCurrentVersion = 0;
-    try {
-      smartBookmarksCurrentVersion = Services.prefs.getIntPref(SMART_BOOKMARKS_PREF);
-    } catch (ex) {}
+    let smartBookmarksCurrentVersion = Services.prefs.getIntPref(SMART_BOOKMARKS_PREF, 0);
 
     // If version is current, or smart bookmarks are disabled, bail out.
     if (smartBookmarksCurrentVersion == -1 ||
diff --git a/application/palemoon/base/content/browser-syncui.js b/application/palemoon/base/content/browser-syncui.js
index 67056e221..6fad03cdd 100644
--- a/application/palemoon/base/content/browser-syncui.js
+++ b/application/palemoon/base/content/browser-syncui.js
@@ -83,10 +83,7 @@ var gSyncUI = {
   _wasDelayed: false,
 
   _needsSetup: function SUI__needsSetup() {
-    let firstSync = "";
-    try {
-      firstSync = Services.prefs.getCharPref("services.sync.firstSync");
-    } catch (e) { }
+    let firstSync = Services.prefs.getCharPref("services.sync.firstSync", "");
     return Weave.Status.checkSetup() == Weave.CLIENT_NOT_CONFIGURED ||
            firstSync == "notReady";
   },
@@ -285,11 +282,7 @@ var gSyncUI = {
     if (!syncButton)
       return;
 
-    let lastSync;
-    try {
-      lastSync = Services.prefs.getCharPref("services.sync.lastSync");
-    }
-    catch (e) { };
+    let lastSync = Services.prefs.getCharPref("services.sync.lastSync");
     if (!lastSync || this._needsSetup()) {
       syncButton.removeAttribute("tooltiptext");
       return;
diff --git a/application/palemoon/base/content/tabbrowser.xml b/application/palemoon/base/content/tabbrowser.xml
index 8ba554cd3..0ca1539f7 100644
--- a/application/palemoon/base/content/tabbrowser.xml
+++ b/application/palemoon/base/content/tabbrowser.xml
@@ -3628,11 +3628,7 @@
           window.addEventListener("resize", this, false);
           window.addEventListener("load", this, false);
 
-          try {
-            this._tabAnimationLoggingEnabled = Services.prefs.getBoolPref("browser.tabs.animationLogging.enabled");
-          } catch (ex) {
-            this._tabAnimationLoggingEnabled = false;
-          }
+          this._tabAnimationLoggingEnabled = Services.prefs.getBoolPref("browser.tabs.animationLogging.enabled", false);
           this._browserNewtabpageEnabled = Services.prefs.getBoolPref("browser.newtabpage.enabled");
         ]]>
       </constructor>
diff --git a/application/palemoon/components/distribution.js b/application/palemoon/components/distribution.js
index d3300604e..121e55b1b 100644
--- a/application/palemoon/components/distribution.js
+++ b/application/palemoon/components/distribution.js
@@ -38,13 +38,7 @@ DistributionCustomizer.prototype = {
   },
 
   get _locale() {
-    let locale;
-    try {
-      locale = this._prefs.getCharPref("general.useragent.locale");
-    }
-    catch (e) {
-      locale = "en-US";
-    }
+    let locale = this._prefs.getCharPref("general.useragent.locale", "en-US");
     this.__defineGetter__("_locale", function() locale);
     return this._locale;
   },
@@ -221,11 +215,7 @@ DistributionCustomizer.prototype = {
         this._ini.getString("Global", "id") + ".bookmarksProcessed";
     }
 
-    let bmProcessed = false;
-    try {
-      bmProcessed = this._prefs.getBoolPref(bmProcessedPref);
-    }
-    catch (e) {}
+    let bmProcessed = this._prefs.getBoolPref(bmProcessedPref, false);
 
     if (!bmProcessed) {
       if (sections["BookmarksMenu"])
diff --git a/application/palemoon/components/feeds/FeedWriter.js b/application/palemoon/components/feeds/FeedWriter.js
index d704835bb..facde5815 100644
--- a/application/palemoon/components/feeds/FeedWriter.js
+++ b/application/palemoon/components/feeds/FeedWriter.js
@@ -18,12 +18,7 @@ function LOG(str) {
   var prefB = Cc["@mozilla.org/preferences-service;1"].
               getService(Ci.nsIPrefBranch);
 
-  var shouldLog = false;
-  try {
-    shouldLog = prefB.getBoolPref("feeds.log");
-  } 
-  catch (ex) {
-  }
+  var shouldLog = prefB.getBoolPref("feeds.log", false);
 
   if (shouldLog)
     dump("*** Feeds: " + str + "\n");
@@ -874,11 +869,7 @@ FeedWriter.prototype = {
         Cc["@mozilla.org/preferences-service;1"].
         getService(Ci.nsIPrefBranch);
 
-    var handler = "bookmarks";
-    try {
-      handler = prefs.getCharPref(getPrefReaderForType(feedType));
-    }
-    catch (ex) { }
+    var handler = prefs.getCharPref(getPrefReaderForType(feedType), "bookmarks");
 
     switch (handler) {
       case "web": {
@@ -1076,11 +1067,7 @@ FeedWriter.prototype = {
         .addEventListener("command", this, false);
 
     // first-run ui
-    var showFirstRunUI = true;
-    try {
-      showFirstRunUI = prefs.getBoolPref(PREF_SHOW_FIRST_RUN_UI);
-    }
-    catch (ex) { }
+    var showFirstRunUI = prefs.getBoolPref(PREF_SHOW_FIRST_RUN_UI, true);
     if (showFirstRunUI) {
       var textfeedinfo1, textfeedinfo2;
       switch (feedType) {
diff --git a/application/palemoon/components/feeds/WebContentConverter.js b/application/palemoon/components/feeds/WebContentConverter.js
index 41679b028..42e2edee0 100644
--- a/application/palemoon/components/feeds/WebContentConverter.js
+++ b/application/palemoon/components/feeds/WebContentConverter.js
@@ -436,13 +436,8 @@ WebContentConverterRegistrar.prototype = {
 
     // check if it is in the black list
     var pb = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
-    var allowed;
-    try {
-      allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "." + aProtocol);
-    }
-    catch (e) {
-      allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "-default");
-    }
+    var allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "." + aProtocol,
+      pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "-default"));
     if (!allowed) {
       // XXX this should be a "security exception" according to spec
       throw("Not allowed to register a protocol handler for " + aProtocol);
diff --git a/application/palemoon/components/nsBrowserContentHandler.js b/application/palemoon/components/nsBrowserContentHandler.js
index 6a75b40f2..e7f1414c2 100644
--- a/application/palemoon/components/nsBrowserContentHandler.js
+++ b/application/palemoon/components/nsBrowserContentHandler.js
@@ -100,20 +100,14 @@ const OVERRIDE_NEW_BUILD_ID = 3;
  *  OVERRIDE_NONE otherwise.
  */
 function needHomepageOverride(prefb) {
-  var savedmstone = null;
-  try {
-    savedmstone = prefb.getCharPref("browser.startup.homepage_override.mstone");
-  } catch (e) {}
+  var savedmstone = prefb.getCharPref("browser.startup.homepage_override.mstone", "");
 
   if (savedmstone == "ignore")
     return OVERRIDE_NONE;
 
   var mstone = Services.appinfo.platformVersion;
 
-  var savedBuildID = null;
-  try {
-    savedBuildID = prefb.getCharPref("browser.startup.homepage_override.buildID");
-  } catch (e) {}
+  var savedBuildID = prefb.getCharPref("browser.startup.homepage_override.buildID", "");
 
   var buildID = Services.appinfo.platformBuildID;
 
@@ -550,10 +544,7 @@ nsBrowserContentHandler.prototype = {
       // URL if we do end up showing an overridePage. This makes it possible
       // to have the overridePage's content vary depending on the version we're
       // upgrading from.
-      let old_mstone = "unknown";
-      try {
-        old_mstone = Services.prefs.getCharPref("browser.startup.homepage_override.mstone");
-      } catch (ex) {}
+      let old_mstone = Services.prefs.getCharPref("browser.startup.homepage_override.mstone", "unknown");
       let override = needHomepageOverride(prefb);
       if (override != OVERRIDE_NONE) {
         switch (override) {
diff --git a/application/palemoon/components/nsBrowserGlue.js b/application/palemoon/components/nsBrowserGlue.js
index 89e966a86..2a6ec3e2c 100644
--- a/application/palemoon/components/nsBrowserGlue.js
+++ b/application/palemoon/components/nsBrowserGlue.js
@@ -993,14 +993,8 @@ BrowserGlue.prototype = {
         // An import operation is about to run.
         // Don't try to recreate smart bookmarks if autoExportHTML is true or
         // smart bookmarks are disabled.
-        var autoExportHTML = false;
-        try {
-          autoExportHTML = Services.prefs.getBoolPref("browser.bookmarks.autoExportHTML");
-        } catch(ex) {}
-        var smartBookmarksVersion = 0;
-        try {
-          smartBookmarksVersion = Services.prefs.getIntPref("browser.places.smartBookmarksVersion");
-        } catch(ex) {}
+        var autoExportHTML = Services.prefs.getBoolPref("browser.bookmarks.autoExportHTML", false);
+        var smartBookmarksVersion = Services.prefs.getIntPref("browser.places.smartBookmarksVersion", 0);
         if (!autoExportHTML && smartBookmarksVersion != -1)
           Services.prefs.setIntPref("browser.places.smartBookmarksVersion", 0);
 
@@ -1559,10 +1553,7 @@ BrowserGlue.prototype = {
     const MAX_RESULTS = 10;
 
     // Get current smart bookmarks version.  If not set, create them.
-    let smartBookmarksCurrentVersion = 0;
-    try {
-      smartBookmarksCurrentVersion = Services.prefs.getIntPref(SMART_BOOKMARKS_PREF);
-    } catch(ex) {}
+    let smartBookmarksCurrentVersion = Services.prefs.getIntPref(SMART_BOOKMARKS_PREF, 0);
 
     // If version is current or smart bookmarks are disabled, just bail out.
     if (smartBookmarksCurrentVersion == -1 ||
diff --git a/devtools/client/framework/devtools.js b/devtools/client/framework/devtools.js
index 90f88023b..976a4b56d 100644
--- a/devtools/client/framework/devtools.js
+++ b/devtools/client/framework/devtools.js
@@ -195,12 +195,7 @@ DevTools.prototype = {
       return tool;
     }
 
-    let enabled;
-    try {
-      enabled = Services.prefs.getBoolPref(tool.visibilityswitch);
-    } catch (e) {
-      enabled = true;
-    }
+    let enabled = Services.prefs.getBoolPref(tool.visibilityswitch, true);
 
     return enabled ? tool : null;
   },
diff --git a/devtools/client/framework/toolbox-process-window.js b/devtools/client/framework/toolbox-process-window.js
index 8ead718b3..8f75e3e24 100644
--- a/devtools/client/framework/toolbox-process-window.js
+++ b/devtools/client/framework/toolbox-process-window.js
@@ -100,17 +100,12 @@ function openToolbox({ form, chrome, isTabActor }) {
   };
   TargetFactory.forRemoteTab(options).then(target => {
     let frame = document.getElementById("toolbox-iframe");
-    let selectedTool = "jsdebugger";
-
-    try {
-      // Remember the last panel that was used inside of this profile.
-      selectedTool = Services.prefs.getCharPref("devtools.toolbox.selectedTool");
-    } catch(e) {}
-
-    try {
-      // But if we are testing, then it should always open the debugger panel.
-      selectedTool = Services.prefs.getCharPref("devtools.browsertoolbox.panel");
-    } catch(e) {}
+    // Remember the last panel that was used inside of this profile.
+    // But if we are testing, then it should always open the debugger panel.
+    let selectedTool =
+      Services.prefs.getCharPref("devtools.browsertoolbox.panel",
+                                 Services.prefs.getCharPref("devtools.toolbox.selectedTool",
+                                                            "jsdebugger"));
 
     let options = { customIframe: frame };
     gDevTools.showToolbox(target,
diff --git a/devtools/client/framework/toolbox.js b/devtools/client/framework/toolbox.js
index 926e30647..cde7de0e4 100644
--- a/devtools/client/framework/toolbox.js
+++ b/devtools/client/framework/toolbox.js
@@ -1131,12 +1131,7 @@ Toolbox.prototype = {
   setToolboxButtonsVisibility: function () {
     this.toolboxButtons.forEach(buttonSpec => {
       let { visibilityswitch, button, isTargetSupported } = buttonSpec;
-      let on = true;
-      try {
-        on = Services.prefs.getBoolPref(visibilityswitch);
-      } catch (ex) {
-        // Do nothing.
-      }
+      let on = Services.prefs.getBoolPref(visibilityswitch, true);
 
       on = on && isTargetSupported(this.target);
 
diff --git a/devtools/client/inspector/markup/markup.js b/devtools/client/inspector/markup/markup.js
index d6e9f8c11..a4b65c899 100644
--- a/devtools/client/inspector/markup/markup.js
+++ b/devtools/client/inspector/markup/markup.js
@@ -73,11 +73,8 @@ function MarkupView(inspector, frame, controllerWindow) {
   this._elt = this.doc.querySelector("#root");
   this.htmlEditor = new HTMLEditor(this.doc);
 
-  try {
-    this.maxChildren = Services.prefs.getIntPref("devtools.markup.pagesize");
-  } catch (ex) {
-    this.maxChildren = DEFAULT_MAX_CHILDREN;
-  }
+  this.maxChildren = Services.prefs.getIntPref("devtools.markup.pagesize",
+                                               DEFAULT_MAX_CHILDREN);
 
   this.collapseAttributes =
     Services.prefs.getBoolPref(ATTR_COLLAPSE_ENABLED_PREF);
diff --git a/devtools/shared/touch/simulator-core.js b/devtools/shared/touch/simulator-core.js
index 6933f9207..fff7d2e78 100644
--- a/devtools/shared/touch/simulator-core.js
+++ b/devtools/shared/touch/simulator-core.js
@@ -18,19 +18,8 @@ var systemAppOrigin = (function () {
   return systemOrigin;
 })();
 
-var threshold = 25;
-try {
-  threshold = Services.prefs.getIntPref("ui.dragThresholdX");
-} catch (e) {
-  // Fall back to default value
-}
-
-var delay = 500;
-try {
-  delay = Services.prefs.getIntPref("ui.click_hold_context_menus.delay");
-} catch (e) {
-  // Fall back to default value
-}
+var threshold = Services.prefs.getIntPref("ui.dragThresholdX", 25);
+var delay = Services.prefs.getIntPref("ui.click_hold_context_menus.delay", 500);
 
 function SimulatorCore(simulatorTarget) {
   this.simulatorTarget = simulatorTarget;
diff --git a/dom/browser-element/BrowserElementChildPreload.js b/dom/browser-element/BrowserElementChildPreload.js
index 780dfa80e..5adff2cac 100644
--- a/dom/browser-element/BrowserElementChildPreload.js
+++ b/dom/browser-element/BrowserElementChildPreload.js
@@ -1010,11 +1010,7 @@ BrowserElementChild.prototype = {
       self._takeScreenshot(maxWidth, maxHeight, mimeType, domRequestID);
     };
 
-    let maxDelayMS = 2000;
-    try {
-      maxDelayMS = Services.prefs.getIntPref('dom.browserElement.maxScreenshotDelayMS');
-    }
-    catch(e) {}
+    let maxDelayMS = Services.prefs.getIntPref('dom.browserElement.maxScreenshotDelayMS', 2000);
 
     // Try to wait for the event loop to go idle before we take the screenshot,
     // but once we've waited maxDelayMS milliseconds, go ahead and take it
@@ -1720,10 +1716,7 @@ BrowserElementChild.prototype = {
                 // certerror? If yes, maybe we should add a property to the
                 // event to to indicate whether there is a custom page. That would
                 // let the embedder have more control over the desired behavior.
-                let errorPage = null;
-                try {
-                  errorPage = Services.prefs.getCharPref(CERTIFICATE_ERROR_PAGE_PREF);
-                } catch (e) {}
+                let errorPage = Services.prefs.getCharPref(CERTIFICATE_ERROR_PAGE_PREF, "");
 
                 if (errorPage == 'certerror') {
                   sendAsyncMsg('error', { type: 'certerror' });
diff --git a/dom/indexedDB/test/test_globalObjects_other.xul b/dom/indexedDB/test/test_globalObjects_other.xul
index eb180a9b4..b527d66bd 100644
--- a/dom/indexedDB/test/test_globalObjects_other.xul
+++ b/dom/indexedDB/test/test_globalObjects_other.xul
@@ -31,14 +31,8 @@
     Cu.import("resource://gre/modules/Services.jsm");
     for (var stage of [ "install", "startup", "shutdown", "uninstall" ]) {
       for (var symbol of [ "IDBKeyRange", "indexedDB" ]) {
-        let pref;
-        try {
-          pref = Services.prefs.getBoolPref("indexeddbtest.bootstrap." + stage +
-                                            "." + symbol);
-        }
-        catch(ex) {
-          pref = false;
-        }
+        let pref = Services.prefs.getBoolPref("indexeddbtest.bootstrap." + stage +
+                                              "." + symbol, false);
         ok(pref, "Symbol '" + symbol + "' present during '" + stage + "'");
       }
     }
diff --git a/dom/presentation/PresentationDataChannelSessionTransport.js b/dom/presentation/PresentationDataChannelSessionTransport.js
index 461e4f2cb..9af6213cb 100644
--- a/dom/presentation/PresentationDataChannelSessionTransport.js
+++ b/dom/presentation/PresentationDataChannelSessionTransport.js
@@ -109,13 +109,7 @@ PresentationTransportBuilder.prototype = {
 
     // TODO bug 1228235 we should have a way to let device providers customize
     // the time-out duration.
-    let timeout;
-    try {
-      timeout = Services.prefs.getIntPref("presentation.receiver.loading.timeout");
-    } catch (e) {
-      // This happens if the pref doesn't exist, so we have a default value.
-      timeout = 10000;
-    }
+    let timeout = Services.prefs.getIntPref("presentation.receiver.loading.timeout", 10000);
 
     // The timer is to check if the negotiation finishes on time.
     this._timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
diff --git a/dom/tests/mochitest/localstorage/test_localStorageQuotaPrivateBrowsing_perwindowpb.html b/dom/tests/mochitest/localstorage/test_localStorageQuotaPrivateBrowsing_perwindowpb.html
index 24d3e4ba3..4dcc361c1 100644
--- a/dom/tests/mochitest/localstorage/test_localStorageQuotaPrivateBrowsing_perwindowpb.html
+++ b/dom/tests/mochitest/localstorage/test_localStorageQuotaPrivateBrowsing_perwindowpb.html
@@ -14,13 +14,7 @@ const Ci = Components.interfaces;
 const CONTENT_PAGE = "http://mochi.test:8888/chrome/dom/tests/mochitest/localstorage/page_blank.html";
 const slavePath = "/chrome/dom/tests/mochitest/localstorage/";
 var currentTest = 1;
-var quota;
-
-try {
-  quota = Services.prefs.getIntPref("dom.storage.default_quota");
-} catch (ex) {
-  quota = 5 * 1024;
-}
+var quota = Services.prefs.getIntPref("dom.storage.default_quota", 5 * 1024);
 Services.prefs.setIntPref("browser.startup.page", 0);
 Services.prefs.setIntPref("dom.storage.default_quota", 1);
 
diff --git a/layout/tools/reftest/reftest.jsm b/layout/tools/reftest/reftest.jsm
index bd9976b0f..c885150a4 100644
--- a/layout/tools/reftest/reftest.jsm
+++ b/layout/tools/reftest/reftest.jsm
@@ -277,29 +277,10 @@ this.OnRefTestLoad = function OnRefTestLoad(win)
 
     var prefs = Components.classes["@mozilla.org/preferences-service;1"].
                 getService(Components.interfaces.nsIPrefBranch);
-    try {
-        gBrowserIsRemote = prefs.getBoolPref("browser.tabs.remote.autostart");
-    } catch (e) {
-        gBrowserIsRemote = false;
-    }
-
-    try {
-        gB2GisMulet = prefs.getBoolPref("b2g.is_mulet");
-    } catch (e) {
-        gB2GisMulet = false;
-    }
-
-    try {
-      gBrowserIsIframe = prefs.getBoolPref("reftest.browser.iframe.enabled");
-    } catch (e) {
-      gBrowserIsIframe = false;
-    }
-
-    try {
-      gLogLevel = prefs.getCharPref("reftest.logLevel");
-    } catch (e) {
-      gLogLevel ='info';
-    }
+    gBrowserIsRemote = prefs.getBoolPref("browser.tabs.remote.autostart", false);
+    gB2GisMulet = prefs.getBoolPref("b2g.is_mulet", false);
+    gBrowserIsIframe = prefs.getBoolPref("reftest.browser.iframe.enabled", false);
+    gLogLevel = prefs.getCharPref("reftest.logLevel", "info");
 
     if (win === undefined || win == null) {
       win = window;
@@ -366,11 +347,7 @@ function InitAndStartRefTests()
     } catch (e) {}
 
     /* set the gLoadTimeout */
-    try {
-        gLoadTimeout = prefs.getIntPref("reftest.timeout");
-    } catch(e) {
-        gLoadTimeout = 5 * 60 * 1000; //5 minutes as per bug 479518
-    }
+    gLoadTimeout = prefs.getIntPref("reftest.timeout", 5 * 60 * 1000); //5 minutes as per bug 479518
 
     /* Get the logfile for android tests */
     try {
@@ -381,27 +358,12 @@ function InitAndStartRefTests()
         }
     } catch(e) {}
 
-    try {
-        gRemote = prefs.getBoolPref("reftest.remote");
-    } catch(e) {
-        gRemote = false;
-    }
-
-    try {
-        gIgnoreWindowSize = prefs.getBoolPref("reftest.ignoreWindowSize");
-    } catch(e) {
-        gIgnoreWindowSize = false;
-    }
+    gRemote = prefs.getBoolPref("reftest.remote", false);
+    gIgnoreWindowSize = prefs.getBoolPref("reftest.ignoreWindowSize", false);
 
     /* Support for running a chunk (subset) of tests.  In separate try as this is optional */
-    try {
-        gTotalChunks = prefs.getIntPref("reftest.totalChunks");
-        gThisChunk = prefs.getIntPref("reftest.thisChunk");
-    }
-    catch(e) {
-        gTotalChunks = 0;
-        gThisChunk = 0;
-    }
+    gTotalChunks = prefs.getIntPref("reftest.totalChunks", 0);
+    gThisChunk = prefs.getIntPref("reftest.thisChunk", 0);
 
     try {
         gFocusFilterMode = prefs.getCharPref("reftest.focusFilterMode");
@@ -468,39 +430,17 @@ function StartTests()
         logger.error("EXCEPTION: " + e);
     }
 
-    try {
-        gNoCanvasCache = prefs.getIntPref("reftest.nocache");
-    } catch(e) {
-        gNoCanvasCache = false;
-    }
-
-    try {
-      gShuffle = prefs.getBoolPref("reftest.shuffle");
-    } catch (e) {
-      gShuffle = false;
-    }
-
-    try {
-      gRunUntilFailure = prefs.getBoolPref("reftest.runUntilFailure");
-    } catch (e) {
-      gRunUntilFailure = false;
-    }
+    gNoCanvasCache = prefs.getIntPref("reftest.nocache", false);
+    gShuffle = prefs.getBoolPref("reftest.shuffle", false);
+    gRunUntilFailure = prefs.getBoolPref("reftest.runUntilFailure", false);
 
     // When we repeat this function is called again, so really only want to set
     // gRepeat once.
     if (gRepeat == null) {
-      try {
-        gRepeat = prefs.getIntPref("reftest.repeat");
-      } catch (e) {
-        gRepeat = 0;
-      }
+      gRepeat = prefs.getIntPref("reftest.repeat", 0);
     }
 
-    try {
-        gRunSlowTests = prefs.getIntPref("reftest.skipslowtests");
-    } catch(e) {
-        gRunSlowTests = false;
-    }
+    gRunSlowTests = prefs.getIntPref("reftest.skipslowtests", false);
 
     if (gShuffle) {
         gNoCanvasCache = true;
@@ -737,11 +677,7 @@ function BuildConditionSandbox(aURL) {
 
     var prefs = CC["@mozilla.org/preferences-service;1"].
                 getService(CI.nsIPrefBranch);
-    try {
-        sandbox.nativeThemePref = !prefs.getBoolPref("mozilla.widget.disable-native-theme");
-    } catch (e) {
-        sandbox.nativeThemePref = true;
-    }
+    sandbox.nativeThemePref = !prefs.getBoolPref("mozilla.widget.disable-native-theme", false);
 
     sandbox.prefs = CU.cloneInto({
         getBoolPref: function(p) { return prefs.getBoolPref(p); },
diff --git a/netwerk/test/unit/test_bug650995.js b/netwerk/test/unit/test_bug650995.js
index 3c1ea8d67..bf2e9fa7d 100644
--- a/netwerk/test/unit/test_bug650995.js
+++ b/netwerk/test/unit/test_bug650995.js
@@ -78,24 +78,14 @@ function InitializeCacheDevices(memDevice, diskDevice) {
     this.start = function() {
         prefService.setBoolPref("browser.cache.memory.enable", memDevice);
         if (memDevice) {
-            try {
-                cap = prefService.getIntPref("browser.cache.memory.capacity");
-            }
-            catch(ex) {
-                cap = 0;
-            }
+            cap = prefService.getIntPref("browser.cache.memory.capacity", 0);
             if (cap == 0) {
                 prefService.setIntPref("browser.cache.memory.capacity", 1024);
             }
         }
         prefService.setBoolPref("browser.cache.disk.enable", diskDevice);
         if (diskDevice) {
-            try {
-                cap = prefService.getIntPref("browser.cache.disk.capacity");
-            }
-            catch(ex) {
-                cap = 0;
-            }
+            cap = prefService.getIntPref("browser.cache.disk.capacity", 0);
             if (cap == 0) {
                 prefService.setIntPref("browser.cache.disk.capacity", 1024);
             }
diff --git a/netwerk/test/unit/test_idn_blacklist.js b/netwerk/test/unit/test_idn_blacklist.js
index 5ca0173bb..aea45d706 100644
--- a/netwerk/test/unit/test_idn_blacklist.js
+++ b/netwerk/test/unit/test_idn_blacklist.js
@@ -121,12 +121,7 @@ const testcases = [
 function run_test() {
     var pbi = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
     var oldProfile = pbi.getCharPref("network.IDN.restriction_profile", "moderate");
-    var oldWhiteListCom;
-    try {
-        oldWhitelistCom = pbi.getBoolPref("network.IDN.whitelist.com");
-    } catch(e) {
-        oldWhitelistCom = false;
-    }
+    var oldWhitelistCom = pbi.getBoolPref("network.IDN.whitelist.com", false);
     var idnService = Cc["@mozilla.org/network/idn-service;1"].getService(Ci.nsIIDNService);
 
     pbi.setCharPref("network.IDN.restriction_profile", "moderate");
diff --git a/netwerk/test/unit/test_idn_urls.js b/netwerk/test/unit/test_idn_urls.js
index 06a53032b..358854093 100644
--- a/netwerk/test/unit/test_idn_urls.js
+++ b/netwerk/test/unit/test_idn_urls.js
@@ -295,12 +295,7 @@ const profiles = ["ASCII", "high", "moderate"];
 function run_test() {
     var pbi = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
     var oldProfile = pbi.getCharPref("network.IDN.restriction_profile", "moderate");
-    var oldWhiteListCom;
-    try {
-        oldWhitelistCom = pbi.getBoolPref("network.IDN.whitelist.com");
-    } catch(e) {
-        oldWhitelistCom = false;
-    }
+    var oldWhitelistCom = pbi.getBoolPref("network.IDN.whitelist.com", false);
     var idnService = Cc["@mozilla.org/network/idn-service;1"].getService(Ci.nsIIDNService);
 
     for (var i = 0; i < profiles.length; ++i) {
diff --git a/services/common/tokenserverclient.js b/services/common/tokenserverclient.js
index b220ab586..ca40f7d93 100644
--- a/services/common/tokenserverclient.js
+++ b/services/common/tokenserverclient.js
@@ -149,10 +149,7 @@ TokenServerClientServerError.prototype._toStringFields = function() {
  */
 this.TokenServerClient = function TokenServerClient() {
   this._log = Log.repository.getLogger("Common.TokenServerClient");
-  let level = "Debug";
-  try {
-    level = Services.prefs.getCharPref(PREF_LOG_LEVEL);
-  } catch (ex) {}
+  let level = Services.prefs.getCharPref(PREF_LOG_LEVEL, "Debug");
   this._log.level = Log.Level[level];
 }
 TokenServerClient.prototype = {
diff --git a/services/crypto/modules/WeaveCrypto.js b/services/crypto/modules/WeaveCrypto.js
index c040c4f6f..d0d5bdb18 100644
--- a/services/crypto/modules/WeaveCrypto.js
+++ b/services/crypto/modules/WeaveCrypto.js
@@ -51,11 +51,7 @@ WeaveCrypto.prototype = {
         this.prefBranch = Services.prefs.getBranch("services.sync.log.");
         this.prefBranch.addObserver("cryptoDebug", this.observer, false);
         this.observer._self = this;
-        try {
-          this.debug = this.prefBranch.getBoolPref("cryptoDebug");
-        } catch (x) {
-          this.debug = false;
-        }
+        this.debug = this.prefBranch.getBoolPref("cryptoDebug", false);
         XPCOMUtils.defineLazyGetter(this, 'encoder', () => new TextEncoder(UTF_LABEL));
         XPCOMUtils.defineLazyGetter(this, 'decoder', () => new TextDecoder(UTF_LABEL, { fatal: true }));
     },
diff --git a/services/sync/modules/status.js b/services/sync/modules/status.js
index a5b8305b4..1233cbe14 100644
--- a/services/sync/modules/status.js
+++ b/services/sync/modules/status.js
@@ -125,12 +125,7 @@ this.Status = {
   resetSync: function resetSync() {
     // Logger setup.
     let logPref = PREFS_BRANCH + "log.logger.status";
-    let logLevel = "Trace";
-    try {
-      logLevel = Services.prefs.getCharPref(logPref);
-    } catch (ex) {
-      // Use default.
-    }
+    let logLevel = Services.prefs.getCharPref(logPref, "Trace");
     this._log.level = Log.Level[logLevel];
 
     this._log.info("Resetting Status.");
diff --git a/toolkit/components/asyncshutdown/AsyncShutdown.jsm b/toolkit/components/asyncshutdown/AsyncShutdown.jsm
index 62ac36f42..9cdf9e126 100644
--- a/toolkit/components/asyncshutdown/AsyncShutdown.jsm
+++ b/toolkit/components/asyncshutdown/AsyncShutdown.jsm
@@ -79,12 +79,8 @@ const DELAY_WARNING_MS = 10 * 1000;
 // Crash the process if shutdown is really too long
 // (allowing for sleep).
 const PREF_DELAY_CRASH_MS = "toolkit.asyncshutdown.crash_timeout";
-var DELAY_CRASH_MS = 60 * 1000; // One minute
-try {
-  DELAY_CRASH_MS = Services.prefs.getIntPref(PREF_DELAY_CRASH_MS);
-} catch (ex) {
-  // Ignore errors
-}
+var DELAY_CRASH_MS = Services.prefs.getIntPref(PREF_DELAY_CRASH_MS,
+                                               60 * 1000); // One minute
 Services.prefs.addObserver(PREF_DELAY_CRASH_MS, function() {
   DELAY_CRASH_MS = Services.prefs.getIntPref(PREF_DELAY_CRASH_MS);
 }, false);
@@ -207,12 +203,7 @@ function log(msg, prefix = "", error = null) {
   }
 }
 const PREF_DEBUG_LOG = "toolkit.asyncshutdown.log";
-var DEBUG_LOG = false;
-try {
-  DEBUG_LOG = Services.prefs.getBoolPref(PREF_DEBUG_LOG);
-} catch (ex) {
-  // Ignore errors
-}
+var DEBUG_LOG = Services.prefs.getBoolPref(PREF_DEBUG_LOG, false);
 Services.prefs.addObserver(PREF_DEBUG_LOG, function() {
   DEBUG_LOG = Services.prefs.getBoolPref(PREF_DEBUG_LOG);
 }, false);
@@ -360,12 +351,7 @@ this.AsyncShutdown = {
    * Access function getPhase. For testing purposes only.
    */
   get _getPhase() {
-    let accepted = false;
-    try {
-      accepted = Services.prefs.getBoolPref("toolkit.asyncshutdown.testing");
-    } catch (ex) {
-      // Ignore errors
-    }
+    let accepted = Services.prefs.getBoolPref("toolkit.asyncshutdown.testing", false);
     if (accepted) {
       return getPhase;
     }
@@ -464,12 +450,7 @@ function getPhase(topic) {
      * notification. For testing purposes only.
      */
     get _trigger() {
-      let accepted = false;
-      try {
-        accepted = Services.prefs.getBoolPref("toolkit.asyncshutdown.testing");
-      } catch (ex) {
-        // Ignore errors
-      }
+      let accepted = Services.prefs.getBoolPref("toolkit.asyncshutdown.testing", false);
       if (accepted) {
         return () => spinner.observe();
       }
diff --git a/toolkit/components/blocklist/nsBlocklistService.js b/toolkit/components/blocklist/nsBlocklistService.js
index 28bfa71bf..f764497ed 100644
--- a/toolkit/components/blocklist/nsBlocklistService.js
+++ b/toolkit/components/blocklist/nsBlocklistService.js
@@ -243,16 +243,7 @@ function getLocale() {
 
 /* Get the distribution pref values, from defaults only */
 function getDistributionPrefValue(aPrefName) {
-  var prefValue = "default";
-
-  var defaults = gPref.getDefaultBranch(null);
-  try {
-    prefValue = defaults.getCharPref(aPrefName);
-  } catch (e) {
-    // use default when pref not found
-  }
-
-  return prefValue;
+  return gPref.getDefaultBranch(null).getCharPref(aPrefName, "default");
 }
 
 /**
diff --git a/toolkit/components/jsdownloads/src/DownloadIntegration.jsm b/toolkit/components/jsdownloads/src/DownloadIntegration.jsm
index 305284749..a6875ec48 100644
--- a/toolkit/components/jsdownloads/src/DownloadIntegration.jsm
+++ b/toolkit/components/jsdownloads/src/DownloadIntegration.jsm
@@ -368,11 +368,7 @@ this.DownloadIntegration = {
    */
   getPreferredDownloadsDirectory: Task.async(function* () {
     let directoryPath = null;
-    let prefValue = 1;
-
-    try {
-      prefValue = Services.prefs.getIntPref("browser.download.folderList");
-    } catch(e) {}
+    let prefValue = Services.prefs.getIntPref("browser.download.folderList", 1);
 
     switch(prefValue) {
       case 0: // Desktop
diff --git a/toolkit/components/nsDefaultCLH.js b/toolkit/components/nsDefaultCLH.js
index a081bae49..affbf75ee 100644
--- a/toolkit/components/nsDefaultCLH.js
+++ b/toolkit/components/nsDefaultCLH.js
@@ -104,13 +104,7 @@ nsDefaultCLH.prototype = {
     // if the pref is missing, ignore the exception
     try {
       var chromeURI = prefs.getCharPref("toolkit.defaultChromeURI");
-
-      var flags = "chrome,dialog=no,all";
-      try {
-        flags = prefs.getCharPref("toolkit.defaultChromeFeatures");
-      }
-      catch (e) { }
-
+      var flags = prefs.getCharPref("toolkit.defaultChromeFeatures", "chrome,dialog=no,all");
       var wwatch = Components.classes["@mozilla.org/embedcomp/window-watcher;1"]
                             .getService(nsIWindowWatcher);
       wwatch.openWindow(null, chromeURI, "_blank",
diff --git a/toolkit/components/osfile/modules/osfile_async_front.jsm b/toolkit/components/osfile/modules/osfile_async_front.jsm
index 93c7e66d6..1d1d7c73f 100644
--- a/toolkit/components/osfile/modules/osfile_async_front.jsm
+++ b/toolkit/components/osfile/modules/osfile_async_front.jsm
@@ -239,10 +239,9 @@ var Scheduler = this.Scheduler = {
    * Prepare to kill the OS.File worker after a few seconds.
    */
   restartTimer: function(arg) {
-    let delay;
-    try {
-      delay = Services.prefs.getIntPref("osfile.reset_worker_delay");
-    } catch(e) {
+    let delay = Services.prefs.getIntPref("osfile.reset_worker_delay", 0);
+
+    if (!delay) {
       // Don't auto-shutdown if we don't have a delay preference set.
       return;
     }
@@ -468,43 +467,25 @@ var Scheduler = this.Scheduler = {
 const PREF_OSFILE_LOG = "toolkit.osfile.log";
 const PREF_OSFILE_LOG_REDIRECT = "toolkit.osfile.log.redirect";
 
-/**
- * Safely read a PREF_OSFILE_LOG preference.
- * Returns a value read or, in case of an error, oldPref or false.
- *
- * @param bool oldPref
- *        An optional value that the DEBUG flag was set to previously.
- */
-function readDebugPref(prefName, oldPref = false) {
-  let pref = oldPref;
-  try {
-    pref = Services.prefs.getBoolPref(prefName);
-  } catch (x) {
-    // In case of an error when reading a pref keep it as is.
-  }
-  // If neither pref nor oldPref were set, default it to false.
-  return pref;
-};
-
 /**
  * Listen to PREF_OSFILE_LOG changes and update gShouldLog flag
  * appropriately.
  */
 Services.prefs.addObserver(PREF_OSFILE_LOG,
   function prefObserver(aSubject, aTopic, aData) {
-    SharedAll.Config.DEBUG = readDebugPref(PREF_OSFILE_LOG, SharedAll.Config.DEBUG);
+    SharedAll.Config.DEBUG = Services.prefs.getBoolPref(PREF_OSFILE_LOG, SharedAll.Config.DEBUG);
     if (Scheduler.launched) {
       // Don't start the worker just to set this preference.
       Scheduler.post("SET_DEBUG", [SharedAll.Config.DEBUG]);
     }
   }, false);
-SharedAll.Config.DEBUG = readDebugPref(PREF_OSFILE_LOG, false);
+SharedAll.Config.DEBUG = Services.prefs.getBoolPref(PREF_OSFILE_LOG, false);
 
 Services.prefs.addObserver(PREF_OSFILE_LOG_REDIRECT,
   function prefObserver(aSubject, aTopic, aData) {
-    SharedAll.Config.TEST = readDebugPref(PREF_OSFILE_LOG_REDIRECT, OS.Shared.TEST);
+    SharedAll.Config.TEST = Services.prefs.getBoolPref(PREF_OSFILE_LOG_REDIRECT, OS.Shared.TEST);
   }, false);
-SharedAll.Config.TEST = readDebugPref(PREF_OSFILE_LOG_REDIRECT, false);
+SharedAll.Config.TEST = Services.prefs.getBoolPref(PREF_OSFILE_LOG_REDIRECT, false);
 
 
 /**
@@ -515,7 +496,7 @@ var nativeWheneverAvailable = true;
 const PREF_OSFILE_NATIVE = "toolkit.osfile.native";
 Services.prefs.addObserver(PREF_OSFILE_NATIVE,
   function prefObserver(aSubject, aTopic, aData) {
-    nativeWheneverAvailable = readDebugPref(PREF_OSFILE_NATIVE, nativeWheneverAvailable);
+    nativeWheneverAvailable = Services.prefs.getBoolPref(PREF_OSFILE_NATIVE, nativeWheneverAvailable);
   }, false);
 
 
@@ -557,10 +538,9 @@ Services.prefs.addObserver(PREF_OSFILE_TEST_SHUTDOWN_OBSERVER,
   function prefObserver() {
     // The temporary phase topic used to trigger the unclosed
     // phase warning.
-    let TOPIC = null;
+    let TOPIC = Services.prefs.getCharPref(PREF_OSFILE_TEST_SHUTDOWN_OBSERVER,
+                                           "");
     try {
-      TOPIC = Services.prefs.getCharPref(
-        PREF_OSFILE_TEST_SHUTDOWN_OBSERVER);
     } catch (x) {
     }
     if (TOPIC) {
diff --git a/toolkit/components/places/PlacesCategoriesStarter.js b/toolkit/components/places/PlacesCategoriesStarter.js
index 560bd486a..bab14db52 100644
--- a/toolkit/components/places/PlacesCategoriesStarter.js
+++ b/toolkit/components/places/PlacesCategoriesStarter.js
@@ -77,11 +77,8 @@ PlacesCategoriesStarter.prototype = {
         break;
       case "idle-daily":
         // Once a week run places.sqlite maintenance tasks.
-        let lastMaintenance = 0;
-        try {
-          lastMaintenance =
-            Services.prefs.getIntPref("places.database.lastMaintenance");
-        } catch (ex) {}
+        let lastMaintenance =
+            Services.prefs.getIntPref("places.database.lastMaintenance", 0);
         let nowSeconds = parseInt(Date.now() / 1000);
         if (lastMaintenance < nowSeconds - MAINTENANCE_INTERVAL_SECONDS) {
           PlacesDBUtils.maintenanceOnIdle();
diff --git a/toolkit/components/places/PlacesRemoteTabsAutocompleteProvider.jsm b/toolkit/components/places/PlacesRemoteTabsAutocompleteProvider.jsm
index d23d5bc6e..c3bc501eb 100644
--- a/toolkit/components/places/PlacesRemoteTabsAutocompleteProvider.jsm
+++ b/toolkit/components/places/PlacesRemoteTabsAutocompleteProvider.jsm
@@ -95,11 +95,7 @@ function observe(subject, topic, data) {
 
     case "nsPref:changed":
       if (data == PREF_SHOW_REMOTE_ICONS) {
-        try {
-          showRemoteIcons = Services.prefs.getBoolPref(PREF_SHOW_REMOTE_ICONS);
-        } catch (_) {
-          showRemoteIcons = true; // no such pref - default is to show the icons.
-        }
+        showRemoteIcons = Services.prefs.getBoolPref(PREF_SHOW_REMOTE_ICONS, true);
       }
       break;
 
diff --git a/toolkit/components/places/UnifiedComplete.js b/toolkit/components/places/UnifiedComplete.js
index ec5f91111..7b63e29bb 100644
--- a/toolkit/components/places/UnifiedComplete.js
+++ b/toolkit/components/places/UnifiedComplete.js
@@ -437,10 +437,7 @@ XPCOMUtils.defineLazyGetter(this, "Prefs", () => {
     store.suggestTyped = prefs.get(...PREF_SUGGEST_HISTORY_ONLYTYPED);
     store.suggestSearches = prefs.get(...PREF_SUGGEST_SEARCHES);
     store.maxCharsForSearchSuggestions = prefs.get(...PREF_MAX_CHARS_FOR_SUGGEST);
-    store.keywordEnabled = true;
-    try {
-      store.keywordEnabled = Services.prefs.getBoolPref("keyword.enabled");
-    } catch (ex) {}
+    store.keywordEnabled = Services.prefs.getBoolPref("keyword.enabled", true);
 
     // If history is not set, onlyTyped value should be ignored.
     if (!store.suggestHistory) {
diff --git a/toolkit/components/places/nsPlacesExpiration.js b/toolkit/components/places/nsPlacesExpiration.js
index 499934362..767a4d345 100644
--- a/toolkit/components/places/nsPlacesExpiration.js
+++ b/toolkit/components/places/nsPlacesExpiration.js
@@ -812,11 +812,8 @@ nsPlacesExpiration.prototype = {
 
   _loadPrefs: Task.async(function* () {
     // Get the user's limit, if it was set.
-    try {
-      // We want to silently fail since getIntPref throws if it does not exist,
-      // and use a default to fallback to.
-      this._urisLimit = this._prefBranch.getIntPref(PREF_MAX_URIS);
-    } catch (ex) { /* User limit not set */ }
+    this._urisLimit = this._prefBranch.getIntPref(PREF_MAX_URIS,
+                                                  PREF_MAX_URIS_NOTSET);
 
     if (this._urisLimit < 0) {
       // Some testing code expects a pref change to be synchronous, so
@@ -874,11 +871,8 @@ nsPlacesExpiration.prototype = {
                                 this._urisLimit);
 
     // Get the expiration interval value.
-    try {
-      // We want to silently fail since getIntPref throws if it does not exist,
-      // and use a default to fallback to.
-      this._interval = this._prefBranch.getIntPref(PREF_INTERVAL_SECONDS);
-    } catch (ex) { /* User interval not set */ }
+    this._interval = this._prefBranch.getIntPref(PREF_INTERVAL_SECONDS,
+                                                 PREF_INTERVAL_SECONDS_NOTSET);
     if (this._interval <= 0) {
       this._interval = PREF_INTERVAL_SECONDS_NOTSET;
     }
diff --git a/toolkit/components/places/tests/unit/test_000_frecency.js b/toolkit/components/places/tests/unit/test_000_frecency.js
index 0a7347a02..64ee86b59 100644
--- a/toolkit/components/places/tests/unit/test_000_frecency.js
+++ b/toolkit/components/places/tests/unit/test_000_frecency.js
@@ -56,14 +56,8 @@ var prefPrefix = "places.frecency.";
 function* task_initializeBucket(bucket) {
   let [cutoffName, weightName] = bucket;
   // get pref values
-  var weight = 0, cutoff = 0;
-  try {
-    weight = prefs.getIntPref(prefPrefix + weightName);
-  } catch (ex) {}
-  try {
-    cutoff = prefs.getIntPref(prefPrefix + cutoffName);
-  } catch (ex) {}
-
+  var weight = prefs.getIntPref(prefPrefix + weightName, 0);
+  var cutoff = prefs.getIntPref(prefPrefix + cutoffName, 0);
   if (cutoff < 1)
     return;
 
diff --git a/toolkit/components/printing/content/printPageSetup.js b/toolkit/components/printing/content/printPageSetup.js
index 31eb1bdd3..6bcd97207 100644
--- a/toolkit/components/printing/content/printPageSetup.js
+++ b/toolkit/components/printing/content/printPageSetup.js
@@ -65,14 +65,7 @@ function initDialog()
 // ---------------------------------------------------
 function isListOfPrinterFeaturesAvailable()
 {
-  var has_printerfeatures = false;
-
-  try {
-    has_printerfeatures = gPrefs.getBoolPref("print.tmp.printerfeatures." + gPrintSettings.printerName + ".has_special_printerfeatures");
-  } catch (ex) {
-  }
-
-  return has_printerfeatures;
+  return gPrefs.getBoolPref("print.tmp.printerfeatures." + gPrintSettings.printerName + ".has_special_printerfeatures", false);
 }
 
 // ---------------------------------------------------
diff --git a/toolkit/components/printing/content/printdialog.js b/toolkit/components/printing/content/printdialog.js
index e5a38ddce..f9ed94bad 100644
--- a/toolkit/components/printing/content/printdialog.js
+++ b/toolkit/components/printing/content/printdialog.js
@@ -79,15 +79,7 @@ function stripTrailingWhitespace(element)
 // ---------------------------------------------------
 function getPrinterDescription(printerName)
 {
-  var s = "";
-
-  try {
-    /* This may not work with non-ASCII test (see bug 235763 comment #16) */
-    s = gPrefs.getCharPref("print.printer_" + printerName + ".printer_description")
-  } catch (e) {
-  }
-
-  return s;
+  return gPrefs.getCharPref("print.printer_" + printerName + ".printer_description", "")
 }
 
 // ---------------------------------------------------
diff --git a/toolkit/components/printing/content/printjoboptions.js b/toolkit/components/printing/content/printjoboptions.js
index 26f3ffd85..098358940 100644
--- a/toolkit/components/printing/content/printjoboptions.js
+++ b/toolkit/components/printing/content/printjoboptions.js
@@ -33,14 +33,7 @@ function checkDouble(element, maxVal)
 // ---------------------------------------------------
 function isListOfPrinterFeaturesAvailable()
 {
-  var has_printerfeatures = false;
-
-  try {
-    has_printerfeatures = gPrefs.getBoolPref("print.tmp.printerfeatures." + gPrintSettings.printerName + ".has_special_printerfeatures");
-  } catch (ex) {
-  }
-
-  return has_printerfeatures;
+  return gPrefs.getBoolPref("print.tmp.printerfeatures." + gPrintSettings.printerName + ".has_special_printerfeatures", false);
 }
 
 // ---------------------------------------------------
diff --git a/toolkit/components/search/current/nsSearchService.js b/toolkit/components/search/current/nsSearchService.js
index 69c1dfb46..532c38d54 100644
--- a/toolkit/components/search/current/nsSearchService.js
+++ b/toolkit/components/search/current/nsSearchService.js
@@ -391,12 +391,7 @@ function isPartnerBuild() {
 
 // Method to determine if we should be using geo-specific defaults
 function geoSpecificDefaultsEnabled() {
-  let geoSpecificDefaults = false;
-  try {
-    geoSpecificDefaults = Services.prefs.getBoolPref("browser.search.geoSpecificDefaults");
-  } catch (e) {}
-
-  return geoSpecificDefaults;
+  return Services.prefs.getBoolPref("browser.search.geoSpecificDefaults", false);
 }
 
 // Some notes on countryCode and region prefs:
@@ -501,11 +496,7 @@ function isUSTimezone() {
 // If it fails we don't touch that pref so isUS() does its normal thing.
 var ensureKnownCountryCode = Task.async(function* (ss) {
   // If we have a country-code already stored in our prefs we trust it.
-  let countryCode;
-  try {
-    countryCode = Services.prefs.getCharPref("browser.search.countryCode");
-  } catch (e) {}
-
+  let countryCode = Services.prefs.getCharPref("browser.search.countryCode", "");
   if (!countryCode) {
     // We don't have it cached, so fetch it. fetchCountryCode() will call
     // storeCountryCode if it gets a result (even if that happens after the
@@ -727,10 +718,7 @@ var fetchRegionDefault = (ss) => new Promise(resolve => {
 
   // Append the optional cohort value.
   const cohortPref = "browser.search.cohort";
-  let cohort;
-  try {
-    cohort = Services.prefs.getCharPref(cohortPref);
-  } catch (e) {}
+  let cohort = Services.prefs.getCharPref(cohortPref, "");
   if (cohort)
     endpoint += "/" + cohort;
 
@@ -994,11 +982,8 @@ function QueryParameter(aName, aValue, aPurpose) {
 function ParamSubstitution(aParamValue, aSearchTerms, aEngine) {
   var value = aParamValue;
 
-  var distributionID = Services.appinfo.distributionID;
-  try {
-    distributionID = Services.prefs.getCharPref(BROWSER_SEARCH_PREF + "distributionID");
-  }
-  catch (ex) { }
+  var distributionID = Services.prefs.getCharPref(BROWSER_SEARCH_PREF + "distributionID",
+                                                Services.appinfo.distributionID || "");
   var official = MOZ_OFFICIAL;
   try {
     if (Services.prefs.getBoolPref(BROWSER_SEARCH_PREF + "official"))
diff --git a/toolkit/components/search/orginal/nsSearchService.js b/toolkit/components/search/orginal/nsSearchService.js
index 5b5ce7a57..1cec5f966 100644
--- a/toolkit/components/search/orginal/nsSearchService.js
+++ b/toolkit/components/search/orginal/nsSearchService.js
@@ -418,12 +418,7 @@ function isPartnerBuild() {
 
 // Method to determine if we should be using geo-specific defaults
 function geoSpecificDefaultsEnabled() {
-  let geoSpecificDefaults = false;
-  try {
-    geoSpecificDefaults = Services.prefs.getBoolPref("browser.search.geoSpecificDefaults");
-  } catch(e) {}
-
-  return geoSpecificDefaults;
+  return Services.prefs.getBoolPref("browser.search.geoSpecificDefaults", false);
 }
 
 // Some notes on countryCode and region prefs:
@@ -528,11 +523,7 @@ function isUSTimezone() {
 // If it fails we don't touch that pref so isUS() does its normal thing.
 var ensureKnownCountryCode = Task.async(function* () {
   // If we have a country-code already stored in our prefs we trust it.
-  let countryCode;
-  try {
-    countryCode = Services.prefs.getCharPref("browser.search.countryCode");
-  } catch(e) {}
-
+  let countryCode = Services.prefs.getCharPref("browser.search.countryCode", "");
   if (!countryCode) {
     // We don't have it cached, so fetch it. fetchCountryCode() will call
     // storeCountryCode if it gets a result (even if that happens after the
@@ -732,10 +723,7 @@ var fetchRegionDefault = () => new Promise(resolve => {
 
   // Append the optional cohort value.
   const cohortPref = "browser.search.cohort";
-  let cohort;
-  try {
-    cohort = Services.prefs.getCharPref(cohortPref);
-  } catch(e) {}
+  let cohort = Services.prefs.getCharPref(cohortPref, "");
   if (cohort)
     endpoint += "/" + cohort;
 
@@ -1034,11 +1022,8 @@ function QueryParameter(aName, aValue, aPurpose) {
 function ParamSubstitution(aParamValue, aSearchTerms, aEngine) {
   var value = aParamValue;
 
-  var distributionID = MOZ_DISTRIBUTION_ID;
-  try {
-    distributionID = Services.prefs.getCharPref(BROWSER_SEARCH_PREF + "distributionID");
-  }
-  catch (ex) { }
+  var distributionID = Services.prefs.getCharPref(BROWSER_SEARCH_PREF + "distributionID",
+                                                MOZ_DISTRIBUTION_ID || "");
   var official = MOZ_OFFICIAL;
   try {
     if (Services.prefs.getBoolPref(BROWSER_SEARCH_PREF + "official"))
diff --git a/toolkit/components/telemetry/UITelemetry.jsm b/toolkit/components/telemetry/UITelemetry.jsm
index bd7a34b72..231b52e23 100644
--- a/toolkit/components/telemetry/UITelemetry.jsm
+++ b/toolkit/components/telemetry/UITelemetry.jsm
@@ -36,11 +36,7 @@ this.UITelemetry = {
     Services.obs.addObserver(this, "profile-before-change", false);
 
     // Pick up the current value.
-    try {
-      this._enabled = Services.prefs.getBoolPref(PREF_ENABLED);
-    } catch (e) {
-      this._enabled = false;
-    }
+    this._enabled = Services.prefs.getBoolPref(PREF_ENABLED, false);
 
     return this._enabled;
   },
diff --git a/toolkit/components/url-classifier/nsUrlClassifierHashCompleter.js b/toolkit/components/url-classifier/nsUrlClassifierHashCompleter.js
index ba4bf225a..5d462c90d 100644
--- a/toolkit/components/url-classifier/nsUrlClassifierHashCompleter.js
+++ b/toolkit/components/url-classifier/nsUrlClassifierHashCompleter.js
@@ -20,12 +20,7 @@ Cu.import("resource://gre/modules/NetUtil.jsm");
 
 // Log only if browser.safebrowsing.debug is true
 function log(...stuff) {
-  let logging = null;
-  try {
-    logging = Services.prefs.getBoolPref("browser.safebrowsing.debug");
-  } catch(e) {
-    return;
-  }
+  let logging = Services.prefs.getBoolPref("browser.safebrowsing.debug", false);
   if (!logging) {
     return;
   }
diff --git a/toolkit/components/urlformatter/tests/unit/test_urlformatter.js b/toolkit/components/urlformatter/tests/unit/test_urlformatter.js
index 393b0dc33..6f218822a 100644
--- a/toolkit/components/urlformatter/tests/unit/test_urlformatter.js
+++ b/toolkit/components/urlformatter/tests/unit/test_urlformatter.js
@@ -27,11 +27,9 @@ function run_test() {
                 QueryInterface(Ci.nsIXULRuntime);
   var abi = macutils && macutils.isUniversalBinary ? "Universal-gcc3" : appInfo.XPCOMABI;
 
-  let channel = "default";
   let defaults = prefs.QueryInterface(Ci.nsIPrefService).getDefaultBranch(null);
-  try {
-    channel = defaults.getCharPref("app.update.channel");
-  } catch (e) {}
+  let channel = defaults.getCharPref("app.update.channel", "default");
+
   // Set distribution values.
   defaults.setCharPref("distribution.id", "bacon");
   defaults.setCharPref("distribution.version", "1.0");
diff --git a/toolkit/content/widgets/browser.xml b/toolkit/content/widgets/browser.xml
index 9c72e86d8..11ed998cc 100644
--- a/toolkit/content/widgets/browser.xml
+++ b/toolkit/content/widgets/browser.xml
@@ -19,14 +19,7 @@
             if (this.getAttribute("autoscroll") == "false")
               return false;
 
-            var enabled = true;
-            try {
-              enabled = this.mPrefs.getBoolPref("general.autoScroll");
-            }
-            catch (ex) {
-            }
-
-            return enabled;
+            return this.mPrefs.getBoolPref("general.autoScroll", true);
           ]]>
         </getter>
       </property>
@@ -1427,18 +1420,8 @@
             return;
 
           // Toggle browse with caret mode
-          var browseWithCaretOn = false;
-          var warn = true;
-
-          try {
-            warn = this.mPrefs.getBoolPref(kPrefWarnOnEnable);
-          } catch (ex) {
-          }
-
-          try {
-            browseWithCaretOn = this.mPrefs.getBoolPref(kPrefCaretBrowsingOn);
-          } catch (ex) {
-          }
+          var browseWithCaretOn = this.mPrefs.getBoolPref(kPrefCaretBrowsingOn, false);
+          var warn = this.mPrefs.getBoolPref(kPrefWarnOnEnable, true);
           if (warn && !browseWithCaretOn) {
             var checkValue = {value:false};
             var promptService = Components.classes["@mozilla.org/embedcomp/prompt-service;1"]
diff --git a/toolkit/content/widgets/preferences.xml b/toolkit/content/widgets/preferences.xml
index 9fb2ac7ea..11de03246 100644
--- a/toolkit/content/widgets/preferences.xml
+++ b/toolkit/content/widgets/preferences.xml
@@ -893,12 +893,8 @@
         <![CDATA[
           var psvc = Components.classes["@mozilla.org/preferences-service;1"]
                                .getService(Components.interfaces.nsIPrefBranch);
-          var animate = /Mac/.test(navigator.platform);
-          try {
-            animate = psvc.getBoolPref("browser.preferences.animateFadeIn");
-          }
-          catch (e) { }
-          return animate;
+          return psvc.getBoolPref("browser.preferences.animateFadeIn",
+                                       /Mac/.test(navigator.platform));
         ]]>
         </getter>
       </property>
diff --git a/toolkit/content/widgets/scrollbox.xml b/toolkit/content/widgets/scrollbox.xml
index ff57a5911..219b7cb5e 100644
--- a/toolkit/content/widgets/scrollbox.xml
+++ b/toolkit/content/widgets/scrollbox.xml
@@ -80,13 +80,8 @@
       <property name="scrollIncrement" readonly="true">
         <getter><![CDATA[
           if (this._scrollIncrement === null) {
-            try {
-              this._scrollIncrement = this._prefBranch
-                                          .getIntPref("toolkit.scrollbox.scrollIncrement");
-            }
-            catch (ex) {
-              this._scrollIncrement = 20;
-            }
+            this._scrollIncrement = this._prefBranch
+                                        .getIntPref("toolkit.scrollbox.scrollIncrement", 20);
           }
           return this._scrollIncrement;
         ]]></getter>
@@ -99,13 +94,8 @@
             if (this.hasAttribute("smoothscroll")) {
               this._smoothScroll = (this.getAttribute("smoothscroll") == "true");
             } else {
-              try {
-                this._smoothScroll = this._prefBranch
-                                         .getBoolPref("toolkit.scrollbox.smoothScroll");
-              }
-              catch (ex) {
-                this._smoothScroll = true;
-              }
+              this._smoothScroll = this._prefBranch
+                                       .getBoolPref("toolkit.scrollbox.smoothScroll", true);
             }
           }
           return this._smoothScroll;
@@ -737,12 +727,9 @@
     </content>
     <implementation implements="nsITimerCallback, nsIDOMEventListener">
       <constructor><![CDATA[
-        try {
-          this._scrollDelay = this._prefBranch
-                                  .getIntPref("toolkit.scrollbox.clickToScroll.scrollDelay");
-        }
-        catch (ex) {
-        }
+        this._scrollDelay = this._prefBranch
+                                .getIntPref("toolkit.scrollbox.clickToScroll.scrollDelay",
+                                            this._scrollDelay);
       ]]></constructor>
 
       <destructor><![CDATA[
diff --git a/toolkit/modules/NewTabUtils.jsm b/toolkit/modules/NewTabUtils.jsm
index 548d87dda..35e38156f 100644
--- a/toolkit/modules/NewTabUtils.jsm
+++ b/toolkit/modules/NewTabUtils.jsm
@@ -119,18 +119,14 @@ LinksStorage.prototype = {
 
   get _storedVersion() {
     if (this.__storedVersion === undefined) {
-      try {
-        this.__storedVersion =
-          Services.prefs.getIntPref("browser.newtabpage.storageVersion");
-      } catch (ex) {
-        // The storage version is unknown, so either:
-        // - it's a new profile
-        // - it's a profile where versioning information got lost
-        // In this case we still run through all of the valid migrations,
-        // starting from 1, as if it was a downgrade.  As previously stated the
-        // migrations should already support running on an updated store.
-        this.__storedVersion = 1;
-      }
+      // The storage version is unknown, so either:
+      // - it's a new profile
+      // - it's a profile where versioning information got lost
+      // In this case we still run through all of the valid migrations,
+      // starting from 1, as if it was a downgrade.  As previously stated the
+      // migrations should already support running on an updated store.
+      this.__storedVersion =
+        Services.prefs.getIntPref("browser.newtabpage.storageVersion", 1);
     }
     return this.__storedVersion;
   },
diff --git a/toolkit/modules/PermissionsUtils.jsm b/toolkit/modules/PermissionsUtils.jsm
index dfed76f0c..4bf43a3ec 100644
--- a/toolkit/modules/PermissionsUtils.jsm
+++ b/toolkit/modules/PermissionsUtils.jsm
@@ -16,10 +16,7 @@ function importPrefBranch(aPrefBranch, aPermission, aAction) {
   let list = Services.prefs.getChildList(aPrefBranch, {});
 
   for (let pref of list) {
-    let origins = "";
-    try {
-      origins = Services.prefs.getCharPref(pref);
-    } catch (e) {}
+    let origins = Services.prefs.getCharPref(pref, "");
 
     if (!origins)
       continue;
diff --git a/toolkit/modules/UpdateUtils.jsm b/toolkit/modules/UpdateUtils.jsm
index e92b1b797..fed7c7637 100644
--- a/toolkit/modules/UpdateUtils.jsm
+++ b/toolkit/modules/UpdateUtils.jsm
@@ -31,13 +31,9 @@ this.UpdateUtils = {
    *        Whether or not to include the partner bits. Default: true.
    */
   getUpdateChannel(aIncludePartners = true) {
-    let channel = AppConstants.MOZ_UPDATE_CHANNEL;
+    let channel = defaults.getCharPref("app.update.channel",
+                                       AppConstants.MOZ_UPDATE_CHANNEL);
     let defaults = Services.prefs.getDefaultBranch(null);
-    try {
-      channel = defaults.getCharPref("app.update.channel");
-    } catch (e) {
-      // use default value when pref not found
-    }
 
     if (aIncludePartners) {
       try {
@@ -93,15 +89,7 @@ this.UpdateUtils = {
 
 /* Get the distribution pref values, from defaults only */
 function getDistributionPrefValue(aPrefName) {
-  var prefValue = "default";
-
-  try {
-    prefValue = Services.prefs.getDefaultBranch(null).getCharPref(aPrefName);
-  } catch (e) {
-    // use default when pref not found
-  }
-
-  return prefValue;
+  return prefValue = Services.prefs.getDefaultBranch(null).getCharPref(aPrefName, "default");
 }
 
 /**
diff --git a/toolkit/modules/secondscreen/SimpleServiceDiscovery.jsm b/toolkit/modules/secondscreen/SimpleServiceDiscovery.jsm
index cf9617ea1..4abc93ad1 100644
--- a/toolkit/modules/secondscreen/SimpleServiceDiscovery.jsm
+++ b/toolkit/modules/secondscreen/SimpleServiceDiscovery.jsm
@@ -186,10 +186,7 @@ var SimpleServiceDiscovery = {
   },
 
   _searchFixedDevices: function _searchFixedDevices() {
-    let fixedDevices = null;
-    try {
-      fixedDevices = Services.prefs.getCharPref("browser.casting.fixedDevices");
-    } catch (e) {}
+    let fixedDevices = Services.prefs.getCharPref("browser.casting.fixedDevices", "");
 
     if (!fixedDevices) {
       return;
diff --git a/toolkit/mozapps/downloads/nsHelperAppDlg.js b/toolkit/mozapps/downloads/nsHelperAppDlg.js
index 58697cc77..27c0fede0 100644
--- a/toolkit/mozapps/downloads/nsHelperAppDlg.js
+++ b/toolkit/mozapps/downloads/nsHelperAppDlg.js
@@ -253,10 +253,7 @@ nsUnknownContentTypeDialog.prototype = {
       if (!aForcePrompt) {
         // Check to see if the user wishes to auto save to the default download
         // folder without prompting. Note that preference might not be set.
-        let autodownload = false;
-        try {
-          autodownload = prefs.getBoolPref(PREF_BD_USEDOWNLOADDIR);
-        } catch (e) { }
+        let autodownload = prefs.getBoolPref(PREF_BD_USEDOWNLOADDIR, false);
 
         if (autodownload) {
           // Retrieve the user's default download directory
diff --git a/toolkit/mozapps/extensions/AddonManager.jsm b/toolkit/mozapps/extensions/AddonManager.jsm
index 4cd2c3d0a..a48e0034f 100644
--- a/toolkit/mozapps/extensions/AddonManager.jsm
+++ b/toolkit/mozapps/extensions/AddonManager.jsm
@@ -135,12 +135,7 @@ var PrefObserver = {
         Services.obs.removeObserver(this, "xpcom-shutdown");
       }
       else if (aTopic == NS_PREFBRANCH_PREFCHANGE_TOPIC_ID) {
-        let debugLogEnabled = false;
-        try {
-          debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED);
-        }
-        catch (e) {
-        }
+        let debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED, false);
         if (debugLogEnabled) {
           parentLogger.level = Log.Level.Debug;
         }
@@ -791,11 +786,7 @@ var AddonManagerInternal = {
       }
       catch (e) { }
 
-      let oldPlatformVersion = null;
-      try {
-        oldPlatformVersion = Services.prefs.getCharPref(PREF_EM_LAST_PLATFORM_VERSION);
-      }
-      catch (e) { }
+      let oldPlatformVersion = Services.prefs.getCharPref(PREF_EM_LAST_PLATFORM_VERSION, "");
 
       if (appChanged !== false) {
         logger.debug("Application has been upgraded");
@@ -808,40 +799,30 @@ var AddonManagerInternal = {
         this.validateBlocklist();
       }
 
-      try {
-        gCheckCompatibility = Services.prefs.getBoolPref(PREF_EM_CHECK_COMPATIBILITY);
-      } catch (e) {}
+      gCheckCompatibility = Services.prefs.getBoolPref(PREF_EM_CHECK_COMPATIBILITY,
+                                                       gCheckCompatibility);
       Services.prefs.addObserver(PREF_EM_CHECK_COMPATIBILITY, this, false);
 
-      try {
-        gStrictCompatibility = Services.prefs.getBoolPref(PREF_EM_STRICT_COMPATIBILITY);
-      } catch (e) {}
+      gStrictCompatibility = Services.prefs.getBoolPref(PREF_EM_STRICT_COMPATIBILITY,
+                                                        gStrictCompatibility);
       Services.prefs.addObserver(PREF_EM_STRICT_COMPATIBILITY, this, false);
 
-      try {
-        let defaultBranch = Services.prefs.getDefaultBranch("");
-        gCheckUpdateSecurityDefault = defaultBranch.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY);
-      } catch(e) {}
+      let defaultBranch = Services.prefs.getDefaultBranch("");
+      gCheckUpdateSecurityDefault = defaultBranch.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY,
+                                                              gCheckUpdateSecurityDefault);
 
-      try {
-        gCheckUpdateSecurity = Services.prefs.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY);
-      } catch (e) {}
+      gCheckUpdateSecurity = Services.prefs.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY,
+                                                        gCheckUpdateSecurity);
       Services.prefs.addObserver(PREF_EM_CHECK_UPDATE_SECURITY, this, false);
 
-      try {
-        gUpdateEnabled = Services.prefs.getBoolPref(PREF_EM_UPDATE_ENABLED);
-      } catch (e) {}
+      gUpdateEnabled = Services.prefs.getBoolPref(PREF_EM_UPDATE_ENABLED, gUpdateEnabled);
       Services.prefs.addObserver(PREF_EM_UPDATE_ENABLED, this, false);
 
-      try {
-        gAutoUpdateDefault = Services.prefs.getBoolPref(PREF_EM_AUTOUPDATE_DEFAULT);
-      } catch (e) {}
+      gAutoUpdateDefault = Services.prefs.getBoolPref(PREF_EM_AUTOUPDATE_DEFAULT,
+                                                      gAutoUpdateDefault);
       Services.prefs.addObserver(PREF_EM_AUTOUPDATE_DEFAULT, this, false);
 
-      let defaultProvidersEnabled = true;
-      try {
-        defaultProvidersEnabled = Services.prefs.getBoolPref(PREF_DEFAULT_PROVIDERS_ENABLED);
-      } catch (e) {}
+      let defaultProvidersEnabled = Services.prefs.getBoolPref(PREF_DEFAULT_PROVIDERS_ENABLED, true);
       AddonManagerPrivate.recordSimpleMeasure("default_providers", defaultProvidersEnabled);
 
       // Ensure all default providers have had a chance to register themselves
@@ -1167,11 +1148,7 @@ var AddonManagerInternal = {
     switch (aData) {
       case PREF_EM_CHECK_COMPATIBILITY: {
         let oldValue = gCheckCompatibility;
-        try {
-          gCheckCompatibility = Services.prefs.getBoolPref(PREF_EM_CHECK_COMPATIBILITY);
-        } catch(e) {
-          gCheckCompatibility = true;
-        }
+        gCheckCompatibility = Services.prefs.getBoolPref(PREF_EM_CHECK_COMPATIBILITY, true);
 
         this.callManagerListeners("onCompatibilityModeChanged");
 
@@ -1182,11 +1159,7 @@ var AddonManagerInternal = {
       }
       case PREF_EM_STRICT_COMPATIBILITY: {
         let oldValue = gStrictCompatibility;
-        try {
-          gStrictCompatibility = Services.prefs.getBoolPref(PREF_EM_STRICT_COMPATIBILITY);
-        } catch(e) {
-          gStrictCompatibility = true;
-        }
+        gStrictCompatibility = Services.prefs.getBoolPref(PREF_EM_STRICT_COMPATIBILITY, true);
 
         this.callManagerListeners("onCompatibilityModeChanged");
 
@@ -1197,11 +1170,7 @@ var AddonManagerInternal = {
       }
       case PREF_EM_CHECK_UPDATE_SECURITY: {
         let oldValue = gCheckUpdateSecurity;
-        try {
-          gCheckUpdateSecurity = Services.prefs.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY);
-        } catch(e) {
-          gCheckUpdateSecurity = true;
-        }
+        gCheckUpdateSecurity = Services.prefs.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY, true);
 
         this.callManagerListeners("onCheckUpdateSecurityChanged");
 
@@ -1212,22 +1181,14 @@ var AddonManagerInternal = {
       }
       case PREF_EM_UPDATE_ENABLED: {
         let oldValue = gUpdateEnabled;
-        try {
-          gUpdateEnabled = Services.prefs.getBoolPref(PREF_EM_UPDATE_ENABLED);
-        } catch(e) {
-          gUpdateEnabled = true;
-        }
+        gUpdateEnabled = Services.prefs.getBoolPref(PREF_EM_UPDATE_ENABLED, true);
 
         this.callManagerListeners("onUpdateModeChanged");
         break;
       }
       case PREF_EM_AUTOUPDATE_DEFAULT: {
         let oldValue = gAutoUpdateDefault;
-        try {
-          gAutoUpdateDefault = Services.prefs.getBoolPref(PREF_EM_AUTOUPDATE_DEFAULT);
-        } catch(e) {
-          gAutoUpdateDefault = true;
-        }
+        gAutoUpdateDefault = Services.prefs.getBoolPref(PREF_EM_AUTOUPDATE_DEFAULT, true);
 
         this.callManagerListeners("onUpdateModeChanged");
         break;
diff --git a/toolkit/mozapps/extensions/DeferredSave.jsm b/toolkit/mozapps/extensions/DeferredSave.jsm
index 89f82b265..f1537fe4b 100644
--- a/toolkit/mozapps/extensions/DeferredSave.jsm
+++ b/toolkit/mozapps/extensions/DeferredSave.jsm
@@ -64,12 +64,7 @@ var PrefObserver = {
      Services.obs.removeObserver(this, "xpcom-shutdown");
    }
    else if (aTopic == NS_PREFBRANCH_PREFCHANGE_TOPIC_ID) {
-     let debugLogEnabled = false;
-     try {
-       debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED);
-     }
-     catch (e) {
-     }
+     let debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED, false);
      if (debugLogEnabled) {
        parentLogger.level = Log.Level.Debug;
      }
diff --git a/toolkit/mozapps/extensions/GMPUtils.jsm b/toolkit/mozapps/extensions/GMPUtils.jsm
index 9e41a7a61..a199b4d86 100644
--- a/toolkit/mozapps/extensions/GMPUtils.jsm
+++ b/toolkit/mozapps/extensions/GMPUtils.jsm
@@ -154,13 +154,7 @@ this.GMPPrefs = {
   get: function(aKey, aDefaultValue, aPlugin) {
     if (aKey === this.KEY_APP_DISTRIBUTION ||
         aKey === this.KEY_APP_DISTRIBUTION_VERSION) {
-      let prefValue = "default";
-      try {
-        prefValue = Services.prefs.getDefaultBranch(null).getCharPref(aKey);
-      } catch (e) {
-        // use default when pref not found
-      }
-      return prefValue;
+      return Services.prefs.getDefaultBranch(null).getCharPref(aKey, "default");
     }
     return Preferences.get(this.getPrefKey(aKey, aPlugin), aDefaultValue);
   },
diff --git a/toolkit/mozapps/extensions/LightweightThemeManager.jsm b/toolkit/mozapps/extensions/LightweightThemeManager.jsm
index 372a9f3b8..a4cbf3833 100644
--- a/toolkit/mozapps/extensions/LightweightThemeManager.jsm
+++ b/toolkit/mozapps/extensions/LightweightThemeManager.jsm
@@ -49,12 +49,7 @@ this.__defineGetter__("_prefs", function prefsGetter() {
 
 this.__defineGetter__("_maxUsedThemes", function maxUsedThemesGetter() {
   delete this._maxUsedThemes;
-  try {
-    this._maxUsedThemes = _prefs.getIntPref("maxUsedThemes");
-  }
-  catch (e) {
-    this._maxUsedThemes = DEFAULT_MAX_USED_THEMES_COUNT;
-  }
+  this._maxUsedThemes = _prefs.getIntPref("maxUsedThemes", DEFAULT_MAX_USED_THEMES_COUNT);
   return this._maxUsedThemes;
 });
 
@@ -719,12 +714,8 @@ var _previewTimerCallback = {
 function _prefObserver(aSubject, aTopic, aData) {
   switch (aData) {
     case "maxUsedThemes":
-      try {
-        _maxUsedThemes = _prefs.getIntPref(aData);
-      }
-      catch (e) {
-        _maxUsedThemes = DEFAULT_MAX_USED_THEMES_COUNT;
-      }
+      _maxUsedThemes = _prefs.getIntPref(aData, DEFAULT_MAX_USED_THEMES_COUNT);
+
       // Update the theme list to remove any themes over the number we keep
       _updateUsedThemes(LightweightThemeManager.usedThemes);
       break;
diff --git a/toolkit/mozapps/extensions/internal/AddonLogging.jsm b/toolkit/mozapps/extensions/internal/AddonLogging.jsm
index f05a6fe6c..ffa92c791 100644
--- a/toolkit/mozapps/extensions/internal/AddonLogging.jsm
+++ b/toolkit/mozapps/extensions/internal/AddonLogging.jsm
@@ -179,12 +179,7 @@ var PrefObserver = {
       Services.obs.removeObserver(this, "xpcom-shutdown");
     }
     else if (aTopic == NS_PREFBRANCH_PREFCHANGE_TOPIC_ID) {
-      try {
-        gDebugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED);
-      }
-      catch (e) {
-        gDebugLogEnabled = false;
-      }
+      gDebugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED, false);
     }
   }
 };
diff --git a/toolkit/mozapps/extensions/internal/AddonRepository.jsm b/toolkit/mozapps/extensions/internal/AddonRepository.jsm
index 76a7528c7..9750e9944 100644
--- a/toolkit/mozapps/extensions/internal/AddonRepository.jsm
+++ b/toolkit/mozapps/extensions/internal/AddonRepository.jsm
@@ -486,14 +486,7 @@ this.AddonRepository = {
     }
 
     let preference = PREF_GETADDONS_CACHE_ENABLED;
-    let enabled = false;
-    try {
-      enabled = Services.prefs.getBoolPref(preference);
-    } catch(e) {
-      logger.warn("cacheEnabled: Couldn't get pref: " + preference);
-    }
-
-    return enabled;
+    return Services.prefs.getBoolPref(preference, false);
   },
 
   // A cache of the add-ons stored in the database
@@ -541,11 +534,7 @@ this.AddonRepository = {
 
   metadataAge: function() {
     let now = Math.round(Date.now() / 1000);
-
-    let lastUpdate = 0;
-    try {
-      lastUpdate = Services.prefs.getIntPref(PREF_METADATA_LASTUPDATE);
-    } catch (e) {}
+    let lastUpdate = Services.prefs.getIntPref(PREF_METADATA_LASTUPDATE, 0);
 
     // Handle clock jumps
     if (now < lastUpdate) {
@@ -555,10 +544,8 @@ this.AddonRepository = {
   },
 
   isMetadataStale: function AddonRepo_isMetadataStale() {
-    let threshold = DEFAULT_METADATA_UPDATETHRESHOLD_SEC;
-    try {
-      threshold = Services.prefs.getIntPref(PREF_METADATA_UPDATETHRESHOLD_SEC);
-    } catch (e) {}
+    let threshold = Services.prefs.getIntPref(PREF_METADATA_UPDATETHRESHOLD_SEC,
+                                              DEFAULT_METADATA_UPDATETHRESHOLD_SEC);
     return (this.metadataAge() > threshold);
   },
 
@@ -1543,10 +1530,8 @@ this.AddonRepository = {
 
   // Create url from preference, returning null if preference does not exist
   _formatURLPref: function AddonRepo_formatURLPref(aPreference, aSubstitutions) {
-    let url = null;
-    try {
-      url = Services.prefs.getCharPref(aPreference);
-    } catch(e) {
+    let url = Services.prefs.getCharPref(aPreference, "");
+    if (!url) {
       logger.warn("_formatURLPref: Couldn't get pref: " + aPreference);
       return null;
     }
@@ -1639,10 +1624,7 @@ var AddonDatabase = {
          // Create a blank addons.json file
          this._saveDBToDisk();
 
-         let dbSchema = 0;
-         try {
-           dbSchema = Services.prefs.getIntPref(PREF_GETADDONS_DB_SCHEMA);
-         } catch (e) {}
+         let dbSchema = Services.prefs.getIntPref(PREF_GETADDONS_DB_SCHEMA, 0);
 
          if (dbSchema < DB_MIN_JSON_SCHEMA) {
            let results = yield new Promise((resolve, reject) => {
diff --git a/toolkit/mozapps/extensions/internal/AddonUpdateChecker.jsm b/toolkit/mozapps/extensions/internal/AddonUpdateChecker.jsm
index c06dca1d5..a475f7f1f 100644
--- a/toolkit/mozapps/extensions/internal/AddonUpdateChecker.jsm
+++ b/toolkit/mozapps/extensions/internal/AddonUpdateChecker.jsm
@@ -608,12 +608,7 @@ function UpdateParser(aId, aUpdateKey, aUrl, aObserver) {
   this.observer = aObserver;
   this.url = aUrl;
 
-  let requireBuiltIn = true;
-  try {
-    requireBuiltIn = Services.prefs.getBoolPref(PREF_UPDATE_REQUIREBUILTINCERTS);
-  }
-  catch (e) {
-  }
+  let requireBuiltIn = Services.prefs.getBoolPref(PREF_UPDATE_REQUIREBUILTINCERTS, true);
 
   logger.debug("Requesting " + aUrl);
   try {
@@ -651,12 +646,7 @@ UpdateParser.prototype = {
     this.request = null;
     this._doneAt = new Error("place holder");
 
-    let requireBuiltIn = true;
-    try {
-      requireBuiltIn = Services.prefs.getBoolPref(PREF_UPDATE_REQUIREBUILTINCERTS);
-    }
-    catch (e) {
-    }
+    let requireBuiltIn = Services.prefs.getBoolPref(PREF_UPDATE_REQUIREBUILTINCERTS, true);
 
     try {
       CertUtils.checkCert(request.channel, !requireBuiltIn);
diff --git a/toolkit/mozapps/extensions/internal/XPIProviderUtils.js b/toolkit/mozapps/extensions/internal/XPIProviderUtils.js
index f2420bd1a..69d774e4a 100644
--- a/toolkit/mozapps/extensions/internal/XPIProviderUtils.js
+++ b/toolkit/mozapps/extensions/internal/XPIProviderUtils.js
@@ -1410,10 +1410,7 @@ this.XPIDatabase = {
     // when a lightweight theme is applied for example)
     text += "\r\n[ThemeDirs]\r\n";
 
-    let dssEnabled = false;
-    try {
-      dssEnabled = Services.prefs.getBoolPref(PREF_EM_DSS_ENABLED);
-    } catch (e) {}
+    let dssEnabled = Services.prefs.getBoolPref(PREF_EM_DSS_ENABLED, false);
 
     let themes = [];
     if (dssEnabled) {
diff --git a/toolkit/mozapps/webextensions/AddonManager.jsm b/toolkit/mozapps/webextensions/AddonManager.jsm
index a3bcbb504..efb33a2a9 100644
--- a/toolkit/mozapps/webextensions/AddonManager.jsm
+++ b/toolkit/mozapps/webextensions/AddonManager.jsm
@@ -156,12 +156,7 @@ var PrefObserver = {
         Services.obs.removeObserver(this, "xpcom-shutdown");
       }
       else if (aTopic == NS_PREFBRANCH_PREFCHANGE_TOPIC_ID) {
-        let debugLogEnabled = false;
-        try {
-          debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED);
-        }
-        catch (e) {
-        }
+        let debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED, false);
         if (debugLogEnabled) {
           parentLogger.level = Log.Level.Debug;
         }
diff --git a/toolkit/mozapps/webextensions/content/extensions.js b/toolkit/mozapps/webextensions/content/extensions.js
index 3159eb1e1..807af2e6f 100644
--- a/toolkit/mozapps/webextensions/content/extensions.js
+++ b/toolkit/mozapps/webextensions/content/extensions.js
@@ -2449,10 +2449,7 @@ var gSearchView = {
       finishSearch();
     });
 
-    var maxRemoteResults = 0;
-    try {
-      maxRemoteResults = Services.prefs.getIntPref(PREF_MAXRESULTS);
-    } catch (e) {}
+    var maxRemoteResults = Services.prefs.getIntPref(PREF_MAXRESULTS, 0);
 
     if (maxRemoteResults <= 0) {
       finishSearch(0);
diff --git a/toolkit/mozapps/webextensions/internal/AddonRepository.jsm b/toolkit/mozapps/webextensions/internal/AddonRepository.jsm
index 7f88d44ad..f67b5c7f2 100644
--- a/toolkit/mozapps/webextensions/internal/AddonRepository.jsm
+++ b/toolkit/mozapps/webextensions/internal/AddonRepository.jsm
@@ -121,25 +121,16 @@ function convertHTMLToPlainText(html) {
 }
 
 function getAddonsToCache(aIds, aCallback) {
-  try {
-    var types = Services.prefs.getCharPref(PREF_GETADDONS_CACHE_TYPES);
-  }
-  catch (e) { }
-  if (!types)
-    types = DEFAULT_CACHE_TYPES;
-
+  var types = Services.prefs.getCharPref(PREF_GETADDONS_CACHE_TYPES, DEFAULT_CACHE_TYPES);
   types = types.split(",");
 
   AddonManager.getAddonsByIDs(aIds, function(aAddons) {
     let enabledIds = [];
+    var preference;
     for (var i = 0; i < aIds.length; i++) {
-      var preference = PREF_GETADDONS_CACHE_ID_ENABLED.replace("%ID%", aIds[i]);
-      try {
-        if (!Services.prefs.getBoolPref(preference))
-          continue;
-      } catch (e) {
-        // If the preference doesn't exist caching is enabled by default
-      }
+      preference = Services.prefs.getBoolPref(PREF_GETADDONS_CACHE_ID_ENABLED.replace("%ID%", aIds[i]), false);
+      if (!preference) 
+        continue;
 
       // The add-ons manager may not know about this ID yet if it is a pending
       // install. In that case we'll just cache it regardless
@@ -477,15 +468,7 @@ this.AddonRepository = {
    * Whether caching is currently enabled
    */
   get cacheEnabled() {
-    let preference = PREF_GETADDONS_CACHE_ENABLED;
-    let enabled = false;
-    try {
-      enabled = Services.prefs.getBoolPref(preference);
-    } catch (e) {
-      logger.warn("cacheEnabled: Couldn't get pref: " + preference);
-    }
-
-    return enabled;
+    return Services.prefs.getBoolPref(PREF_GETADDONS_CACHE_ENABLED, false);
   },
 
   // A cache of the add-ons stored in the database
@@ -534,10 +517,7 @@ this.AddonRepository = {
   metadataAge: function() {
     let now = Math.round(Date.now() / 1000);
 
-    let lastUpdate = 0;
-    try {
-      lastUpdate = Services.prefs.getIntPref(PREF_METADATA_LASTUPDATE);
-    } catch (e) {}
+    let lastUpdate = Services.prefs.getIntPref(PREF_METADATA_LASTUPDATE, 0);
 
     // Handle clock jumps
     if (now < lastUpdate) {
@@ -547,10 +527,8 @@ this.AddonRepository = {
   },
 
   isMetadataStale: function() {
-    let threshold = DEFAULT_METADATA_UPDATETHRESHOLD_SEC;
-    try {
-      threshold = Services.prefs.getIntPref(PREF_METADATA_UPDATETHRESHOLD_SEC);
-    } catch (e) {}
+    let threshold = Services.prefs.getIntPref(PREF_METADATA_UPDATETHRESHOLD_SEC,
+                                              DEFAULT_METADATA_UPDATETHRESHOLD_SEC);
     return (this.metadataAge() > threshold);
   },
 
@@ -1507,10 +1485,8 @@ this.AddonRepository = {
 
   // Create url from preference, returning null if preference does not exist
   _formatURLPref: function(aPreference, aSubstitutions) {
-    let url = null;
-    try {
-      url = Services.prefs.getCharPref(aPreference);
-    } catch (e) {
+    let url = Services.prefs.getCharPref(aPreference, "");
+    if (!url) {
       logger.warn("_formatURLPref: Couldn't get pref: " + aPreference);
       return null;
     }
@@ -1604,10 +1580,7 @@ var AddonDatabase = {
          // Create a blank addons.json file
          this._saveDBToDisk();
 
-         let dbSchema = 0;
-         try {
-           dbSchema = Services.prefs.getIntPref(PREF_GETADDONS_DB_SCHEMA);
-         } catch (e) {}
+         let dbSchema = Services.prefs.getIntPref(PREF_GETADDONS_DB_SCHEMA, 0);
 
          if (dbSchema < DB_MIN_JSON_SCHEMA) {
            let results = yield new Promise((resolve, reject) => {
diff --git a/toolkit/mozapps/webextensions/internal/XPIProviderUtils.js b/toolkit/mozapps/webextensions/internal/XPIProviderUtils.js
index 63ff6d8c8..b3682a0b5 100644
--- a/toolkit/mozapps/webextensions/internal/XPIProviderUtils.js
+++ b/toolkit/mozapps/webextensions/internal/XPIProviderUtils.js
@@ -1468,10 +1468,7 @@ this.XPIDatabase = {
     // when a lightweight theme is applied for example)
     text += "\r\n[ThemeDirs]\r\n";
 
-    let dssEnabled = false;
-    try {
-      dssEnabled = Services.prefs.getBoolPref(PREF_EM_DSS_ENABLED);
-    } catch (e) {}
+    let dssEnabled = Services.prefs.getBoolPref(PREF_EM_DSS_ENABLED, false);
 
     let themes = [];
     if (dssEnabled) {
diff --git a/uriloader/exthandler/nsHandlerService.js b/uriloader/exthandler/nsHandlerService.js
index c932f9f5d..5e6356ac2 100644
--- a/uriloader/exthandler/nsHandlerService.js
+++ b/uriloader/exthandler/nsHandlerService.js
@@ -352,17 +352,11 @@ HandlerService.prototype = {
       var prefSvc = Cc["@mozilla.org/preferences-service;1"].
                     getService(Ci.nsIPrefService);
       var prefBranch = prefSvc.getBranch("network.protocol-handler.");
-      try {
-        alwaysAsk = prefBranch.getBoolPref("warn-external." + type);
-      } catch (e) {
-        // will throw if pref didn't exist.
-        try {
-          alwaysAsk = prefBranch.getBoolPref("warn-external-default");
-        } catch (e) {
-          // Nothing to tell us what to do, so be paranoid and prompt.
-          alwaysAsk = true;
-        }
-      }
+      // If neither of the prefs exists, be paranoid and prompt.
+      alwaysAsk =
+        prefBranch.getBoolPref("warn-external." + type,
+                               prefBranch.getBoolPref("warn-external-default",
+                                                      true));
     }
     aHandlerInfo.alwaysAskBeforeHandling = alwaysAsk;