Handle XMLHttpRequest with bad status in Safari's i18n code

safari/ext/common.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2013 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 133 matching lines @@
       xhr.open("GET", safari.extension.baseURI + "_locales/" + locale + "/messages.json", false);
 
       try {
         xhr.send();
       }
       catch (e)
       {
         return null;
       }
 
+      if (xhr.status != 200 && xhr.status != 0)
+        return null;
+
       return JSON.parse(xhr.responseText);
     },
     getMessage: function(msgId, substitutions)
     {
       if (msgId == "@@ui_locale")
         return this._uiLocale;
 
       for (var i = 0; i < this._localeCandidates.length; i++)
       {
         var catalog = this._getCatalog(this._localeCandidates[i]);
@@ skipping 45 matching lines @@
   /* API */
 
   ext = {
     getURL: function(path)
     {
       return safari.extension.baseURI + path;
     },
     i18n: new I18n()
   };
 })();