[gnome-shell] Fix problem when background settings change multiple times in rapid succession

[Owen Taylor <otaylor src gnome org>]

commit 8096e71c536781759a58efb3c9aa56f150c17f7e
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Thu Sep 4 10:01:52 2014 -0400

    Fix problem when background settings change multiple times in rapid succession
    
    The code that cleaned up when a background actor was destroyed tried to access
    the Background as backgroundActor.background._delegate but when the destroy
    signal is emitted, the MetaBackgroundActor was already disposed and
    backgroundActor.background NULL.

 js/ui/background.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/background.js b/js/ui/background.js
index ea5cae4..00b9d63 100644
--- a/js/ui/background.js
+++ b/js/ui/background.js
@@ -701,7 +701,7 @@ const BackgroundManager = new Lang.Class({
                 background.disconnect(changeSignalId);
 
             if (backgroundActor.loadedSignalId)
-                backgroundActor.background._delegate.disconnect(backgroundActor.loadedSignalId);
+                background.disconnect(backgroundActor.loadedSignalId);
         }));
 
         return backgroundActor;