fix a crash-on-exit

meta_frames_destroy() was not safe to be called multiple times, which
was causing a crash on exit due to something else changing somewhere
that makes it get called multiple times.

https://bugzilla.gnome.org/show_bug.cgi?id=654489

upstream commit:
https://gitlab.gnome.org/GNOME/metacity/commit/e35be641

1 files changed, 9 insertions, 0 deletions

diff --git a/src/ui/frames.c b/src/ui/frames.c
index ebf46392..6d0d5aa1 100644
--- a/src/ui/frames.c
+++ b/src/ui/frames.c
@@ -303,8 +303,17 @@ meta_frames_destroy (GtkWidget *widget)
     }
   g_slist_free (winlist);
 
+  if (frames->normal_style)
+    {
   g_object_unref (frames->normal_style);
+      frames->normal_style = NULL;
+    }
+
+  if (frames->style_variants)
+    {
   g_hash_table_destroy (frames->style_variants);
+      frames->style_variants = NULL;
+    }
 
   GTK_WIDGET_CLASS (meta_frames_parent_class)->destroy (widget);
 }