Issue 5510 - Call onerror in case of error

lib/compat.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present 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 307 matching lines @@
       this.responseText = result.responseText;
       this._responseHeaders = result.responseHeaders;
       this.readyState = 4;
 
       // Notify event listeners
       const NS_OK = 0;
       var eventName = (this.channel.status == NS_OK ? "load" : "error");
       var event = {type: eventName};
 
       if (this["on" + eventName])
-        this.onload.call(this, event);
+        this["on" + eventName].call(this, event);
 
       var list = this["_" + eventName + "Handlers"];
       for (var i = 0; i < list.length; i++)
         list[i].call(this, event);
     }.bind(this);
     // HACK (#5066): the code checking whether the connection is allowed is temporary,
     // the actual check should be in the core when we make a decision whether
     // to update a subscription with current connection or not, thus whether to
     // even construct XMLHttpRequest object or not.
     _isSubscriptionDownloadAllowed(function(isAllowed)
@@ skipping 95 matching lines @@
         var kValue = o[k];
         if (predicate.call(thisArg, kValue, k, o)) {
           return kValue;
         }
         // e. Increase k by 1.
         k++;
       }
     }
   });
 }