[metacity] iconcache: don't crash on a non-alpha mask pixmap

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 3bd1a010f9f787f3d5e3bfb309d68e413734518b
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Mon Mar 21 18:49:55 2011 -0400

    iconcache: don't crash on a non-alpha mask pixmap
    
    We assume when applying a mask that it is a depth-1 pixmap that
    cairo interprets as alpha. So ignore a non-depth-1 mask.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=641975

 src/core/iconcache.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)
---
diff --git a/src/core/iconcache.c b/src/core/iconcache.c
index 4647ca8..8c5b9ca 100644
--- a/src/core/iconcache.c
+++ b/src/core/iconcache.c
@@ -432,10 +432,11 @@ try_pixmap_and_mask (MetaDisplay *display,
 
   if (unscaled && src_mask != None)
     {
-      get_pixmap_geometry (display, src_mask, &w, &h, NULL);
-      mask = meta_gdk_pixbuf_get_from_pixmap (src_mask,
-                                              0, 0,
-                                              w, h);
+      get_pixmap_geometry (display, src_mask, &w, &h, &d);
+      if (d == 1)
+        mask = meta_gdk_pixbuf_get_from_pixmap (src_mask,
+                                                0, 0,
+                                                w, h);
     }
 
   meta_error_trap_pop (display, FALSE);