Merge pull request #2668 from vyv03354/bug834075

Handle the error in case the sender is already unloaded

extensions/firefox/components/PdfStreamConverter.js

@@ -473,7 +473,13 @@ RequestListener.prototype.receive = function(event) {
       response = null;
     } else {
       response = function sendResponse(response) {
+        try {
           message.setUserData('response', response, null);
+        } catch (e) {
+          // message is no longer accessible because the sender is already
+          // gone. the unloaded sender cannot receive the response anyway.
+          return false;
+        }
 
         var listener = doc.createEvent('HTMLEvents');
         listener.initEvent('pdf.js.response', true, false);