From efc35545c7f5cd36461b26a946d95a69ecba1413 Mon Sep 17 00:00:00 2001
From: petetnt <pete.a.nykanen@gmail.com>
Date: Wed, 28 Jun 2017 16:34:42 +0300
Subject: [PATCH] Fix NavigationProvider throwing errors when doc.file is
 missing. Fixes #13491

Signed-off-by: petetnt <pete.a.nykanen@gmail.com>
---
 .../default/NavigationAndHistory/NavigationProvider.js     | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/extensions/default/NavigationAndHistory/NavigationProvider.js b/src/extensions/default/NavigationAndHistory/NavigationProvider.js
index 59e713c823c..07e4cbb12ef 100644
--- a/src/extensions/default/NavigationAndHistory/NavigationProvider.js
+++ b/src/extensions/default/NavigationAndHistory/NavigationProvider.js
@@ -481,8 +481,10 @@ define(function (require, exports, module) {
     */
     function _handleExternalChange(evt, doc) {
         if (doc) {
-            _removeBackwardFramesForFile(doc.file);
-            _removeForwardFramesForFile(doc.file);
+            if (doc.file) {
+              _removeBackwardFramesForFile(doc.file);
+	      _removeForwardFramesForFile(doc.file);
+	    }
             _validateNavigationCmds();
         }
     }
@@ -549,3 +551,4 @@ define(function (require, exports, module) {
     
     exports.init = init;
 });
+