Issue 6496 - Account for notifications.create() failing asynchronously

lib/subscriptionInit.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 127 matching lines @@
 function supportsNotificationsWithButtons()
 {
   // Microsoft Edge (as of EdgeHTML 16) doesn't have the notifications API.
   // Opera gives an asynchronous error when buttons are provided (we cannot
   // detect that behavior without attempting to show a notification).
   if (!("notifications" in browser) || info.application == "opera")
     return false;
 
   // Firefox throws synchronously if the "buttons" option is provided.
   // If buttons are supported (i.e. on Chrome), this fails with
-  // a different error message due to missing required options.
+  // an asynchronous error due to missing required options.
   // https://bugzilla.mozilla.org/show_bug.cgi?id=1190681
   try
   {
-    browser.notifications.create({buttons: []});
+    browser.notifications.create({buttons: []}).catch(() => {});
   }
   catch (e)
   {
     if (e.toString().includes('"buttons" is unsupported'))
       return false;
   }
 
   return true;
 }
 
@@ skipping 121 matching lines @@
  * Sets a callback that is called with an array of subscriptions to be added
  * during initialization. The callback must return an array of subscriptions
  * that will effectively be added.
  *
  * @param {function} callback
  */
 exports.setSubscriptionsCallback = callback =>
 {
   subscriptionsCallback = callback;
 };