[gnome-shell] WorkspaceThumbnail: fix typo in stacking code

[Giovanni Campagna <gcampagna src gnome org>]

commit f3df62f27e2afc62be7cb810dfe9e918b02ce09f
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Wed Feb 20 01:44:09 2013 +0100

    WorkspaceThumbnail: fix typo in stacking code
    
    Was causing thumbnails to be below the background.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=694227

 js/ui/workspaceThumbnail.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/workspaceThumbnail.js b/js/ui/workspaceThumbnail.js
index f908777..c2a415a 100644
--- a/js/ui/workspaceThumbnail.js
+++ b/js/ui/workspaceThumbnail.js
@@ -425,7 +425,7 @@ const WorkspaceThumbnail = new Lang.Class({
         this._contents.add_actor(clone.actor);
 
         if (this._windows.length == 0)
-            clone.setStackAbove(this._bgManager.actor);
+            clone.setStackAbove(this._bgManager.background.actor);
         else
             clone.setStackAbove(this._windows[this._windows.length - 1].actor);