Issue 6914 - Wrap window.frameElement in try catch to silence Microsoft Edge exception

inject.preload.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 339 matching lines @@
 
     if ("RTCPeerConnection" in window)
       window.RTCPeerConnection = boundWrappedRTCPeerConnection;
     if ("webkitRTCPeerConnection" in window)
       window.webkitRTCPeerConnection = boundWrappedRTCPeerConnection;
   }
 }
 
 if (document instanceof HTMLDocument)
 {
-  let sandbox = window.frameElement &&
-                window.frameElement.getAttribute("sandbox");
+  let sandbox;
+
+  // We have to wrap the following code in a try catch
+  // because of this Microsoft Edge bug:
+  // https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/19082980/
+  try
+  {
+    sandbox = window.frameElement &&
+              window.frameElement.getAttribute("sandbox");
+  }
+  catch (e) {}
 
   if (typeof sandbox != "string" || /(^|\s)allow-scripts(\s|$)/i.test(sandbox))
   {
     let script = document.createElement("script");
     let code = "(" + injected + ")('" + randomEventName + "');";
 
     script.type = "application/javascript";
     script.async = false;
 
     // Firefox 58 only bypasses site CSPs when assigning to 'src',
     // while Chrome 67 only bypasses site CSPs when using 'textContent'.
     if (browser.runtime.getURL("").startsWith("chrome-extension://"))
     {
       script.textContent = code;
       document.documentElement.appendChild(script);
     }
     else
     {
       let url = URL.createObjectURL(new Blob([code]));
       script.src = url;
       document.documentElement.appendChild(script);
       URL.revokeObjectURL(url);
     }
 
     document.documentElement.removeChild(script);
   }
 }