Issue 1864 - Fixed error caused when generated filters match hidden elements

include.postload.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 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 38 matching lines @@
 }
 
 function highlightElement(element, shadowColor, backgroundColor)
 {
   unhighlightElement(element);
 
   var highlightWithOverlay = function()
   {
     var overlay = addElementOverlay(element);
 
+    // If the element isn't displayed no overlay will be added.
+    // Moreover, we don't need to highlight anything then.
+    if (!overlay)
+      return;
+
     highlightElement(overlay, shadowColor, backgroundColor);
     overlay.style.pointerEvents = "none";
 
     element._unhighlight = function()
     {
       overlay.parentNode.removeChild(overlay);
     };
   };
 
   var highlightWithStyleAttribute = function()
@@ skipping 660 matching lines @@
           lastRightClickEventValid = false;
         else
           lastRightClickEvent = null;
         break;
     }
   });
 
   if (window == window.top)
     ext.backgroundPage.sendMessage({type: "report-html-page"});
 }