From be76181e3743e10fb66bdc5ce4e37784cf0ba9df Mon Sep 17 00:00:00 2001
From: janekptacijarabaci <janekptacijarabaci@seznam.cz>
Date: Mon, 4 Sep 2017 08:57:50 +0200
Subject: [PATCH] Preferences - the blocklist - level - throws an error

---
 browser/components/preferences/preferences.xul | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/browser/components/preferences/preferences.xul b/browser/components/preferences/preferences.xul
index b3f9cf9c46..c30fba8f5f 100644
--- a/browser/components/preferences/preferences.xul
+++ b/browser/components/preferences/preferences.xul
@@ -55,7 +55,7 @@
             style="&prefWinMinSize.styleGNOME;"
 #endif
 #endif
-            onunload="gSecurityPane.syncAddonSecurityLevel();">
+            onunload="if (typeof gSecurityPane != 'undefined') gSecurityPane.syncAddonSecurityLevel();">
 
     <script type="application/javascript" src="chrome://browser/content/utilityOverlay.js"/>