[gnome-shell] layout: Clean up consoleBackgroundGroup

[Jasper St. Pierre <jstpierre src gnome org>]

commit b4678a1cee55ecc029879762f53ce29504aa3957
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Tue Feb 19 20:31:56 2013 -0500

    layout: Clean up consoleBackgroundGroup
    
    We shouldn't leave a reference to a destroyed actor just hanging
    around.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=694227

 js/ui/layout.js |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/js/ui/layout.js b/js/ui/layout.js
index 994d79c..4d5dd49 100644
--- a/js/ui/layout.js
+++ b/js/ui/layout.js
@@ -607,6 +607,8 @@ const LayoutManager = new Lang.Class({
         global.stage_input_mode = Shell.StageInputMode.NORMAL;
 
         this._consoleBackgroundGroup.destroy();
+        this._consoleBackgroundGroup = null;
+
         this._startingUp = false;
 
         this.trayBox.show();