[mutter/wayland] window-actor: Guard against %NULL frame mask

[Rui Matos <rtcm src gnome org>]

commit 94f39a493ffe24013d38c47ef7659218e0f91de5
Author: Florian Müllner <fmuellner gnome org>
Date:   Fri Jan 10 06:26:57 2014 -0500

    window-actor: Guard against %NULL frame mask
    
    Creating a new cogl texture may fail, in which case the intent to
    free it will crash. While something is clearly wrong (insanely
    large window, oom, ...), crashing the WM is harsh and we should
    try to avoid it if at all possible, so carry on.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=722266

 src/compositor/meta-window-actor.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/compositor/meta-window-actor.c b/src/compositor/meta-window-actor.c
index cf62d99..a26d342 100644
--- a/src/compositor/meta-window-actor.c
+++ b/src/compositor/meta-window-actor.c
@@ -1714,7 +1714,8 @@ build_and_scan_frame_mask (MetaWindowActor       *self,
     }
 
   meta_shaped_texture_set_mask_texture (stex, mask_texture);
-  cogl_object_unref (mask_texture);
+  if (mask_texture)
+    cogl_object_unref (mask_texture);
 
   g_free (mask_data);
 }