[gnome-control-center] background: Don't access possibly invalid object

[Debarshi Ray <debarshir src gnome org>]

commit cc17b9d4714569b6057d7267d704c147a5ee41d4
Author: Debarshi Ray <debarshir gnome org>
Date:   Fri Sep 6 17:51:58 2013 +0200

    background: Don't access possibly invalid object
    
    The previous value of CURRENT_BG may not be valid after a call to
    update_preview.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=707569

 panels/background/cc-background-panel.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/panels/background/cc-background-panel.c b/panels/background/cc-background-panel.c
index 8de6e23..9a34f50 100644
--- a/panels/background/cc-background-panel.c
+++ b/panels/background/cc-background-panel.c
@@ -596,6 +596,7 @@ copy_finished_cb (GObject      *source_object,
       char *filename;
 
       update_preview (priv, settings, item);
+      current_background = CURRENT_BG;
 
       /* Save the source XML if there is one */
       filename = get_save_path (SAVE_PATH);