From 0afbb98f42c4037f05f10099c10f9df0ee853a7a Mon Sep 17 00:00:00 2001
From: gorhill <rhill@raymondhill.net>
Date: Thu, 25 Jun 2015 09:05:24 -0400
Subject: [PATCH] this fixes #399

---
 platform/firefox/vapi-background.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/platform/firefox/vapi-background.js b/platform/firefox/vapi-background.js
index 3d73648b5..647c4c407 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -908,6 +908,12 @@ var tabWatcher = (function() {
 
     var currentBrowser = function() {
         var win = Services.wm.getMostRecentWindow('navigator:browser');
+        // https://github.com/gorhill/uBlock/issues/399
+        // getTabBrowser() can return null at browser launch time.
+        var tabBrowser = getTabBrowser(win);
+        if ( tabBrowser === null ) {
+            return null;
+        }
         return browserFromTarget(getTabBrowser(win).selectedTab);
     };