[mutter] meta-window-group: Fix previous commit

[Rico Tzschichholz <ricotz src gnome org>]

commit 90a3d613ca4dad1d2b6f3ffc641092461c69c128
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Thu Jul 18 16:33:50 2013 +0200

    meta-window-group: Fix previous commit

 src/compositor/meta-window-group.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/compositor/meta-window-group.c b/src/compositor/meta-window-group.c
index 525f987..ec22af3 100644
--- a/src/compositor/meta-window-group.c
+++ b/src/compositor/meta-window-group.c
@@ -155,7 +155,8 @@ meta_window_group_paint (ClutterActor *actor)
       if (!CLUTTER_ACTOR_IS_VISIBLE (child))
         continue;
 
-      if (META_WINDOW_ACTOR (child) == info->unredirected_window)
+      if (info->unredirected_window != NULL &&
+          child == CLUTTER_ACTOR (info->unredirected_window))
         continue;
 
       /* If an actor has effects applied, then that can change the area