[mutter] ui: Fix undefined variable warning

[Jasper St. Pierre <jstpierre src gnome org>]

commit 656fe49dbeaa88f65e0b44c66d9434dc73468adc
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Thu Mar 12 13:03:28 2015 -0700

    ui: Fix undefined variable warning
    
    gcc is super smart and notices that we don't have a default case here.

 src/ui/theme.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/ui/theme.c b/src/ui/theme.c
index 4aff7e0..243d369 100644
--- a/src/ui/theme.c
+++ b/src/ui/theme.c
@@ -656,6 +656,7 @@ get_button_rect (MetaButtonType           type,
       *rect = fgeom->appmenu_rect.visible;
       break;
 
+    default:
     case META_BUTTON_TYPE_LAST:
       g_assert_not_reached ();
       break;