Issue 6808 - Default to top frame of page if parent can't be found

ext/background.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 142 matching lines @@
         // overridden when Chrome automatically resets them on navigation.
         if (browser.runtime.lastError)
           ext.pages.onLoading._dispatch(page);
       });
     }
 
     // Update frame URL and parent in frame structure
     let frame = createFrame(tabId, frameId);
     frame.url = new URL(url);
 
-    let parentFrame = framesOfTabs.get(tabId).get(parentFrameId);
+    let frames = framesOfTabs.get(tabId);
+    let parentFrame = frames.get(parentFrameId);
+    if (!parentFrame && parentFrameId > 0)
+      parentFrame = frames.get(0);
+
     if (parentFrame)
       frame.parent = parentFrame;
   }
 
   browser.webRequest.onHeadersReceived.addListener(details =>
   {
     // We have to update the frame structure when switching to a new
     // document, so that we process any further requests made by that
     // document in the right context. Unfortunately, we cannot rely
     // on webNavigation.onCommitted since it isn't guaranteed to fire
@@ skipping 347 matching lines @@
         {
           let frames = new Map();
           framesOfTabs.set(tab.id, frames);
 
           for (let detail of details)
           {
             let frame = {url: new URL(detail.url)};
             frames.set(detail.frameId, frame);
 
             if (detail.parentFrameId != -1)
+            {
               frame.parent = frames.get(detail.parentFrameId);
+
+              if (!frame.parent && detail.parentFrameId > 0)
+                frame.parent = frames.get(0);
+            }
           }
         }
       });
     });
   });
 
 
   /* Message passing */
 
   browser.runtime.onMessage.addListener((message, rawSender, sendResponse) =>
@@ skipping 48 matching lines @@
           return frames.get(0) || null;
         }
       };
     }
 
     return ext.onMessage._dispatch(
       message, sender, sendResponse
     ).includes(true);
   });
 }