[mutter] window: Warn if try to focus unmanaging windows

[Jonas Ådahl <jadahl src gnome org>]

commit e14613e74e8c9bb8e08dc7a94e35a86c8baf7a01
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Thu Feb 14 13:57:22 2019 +0100

    window: Warn if try to focus unmanaging windows
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/307

 src/core/window.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/core/window.c b/src/core/window.c
index 1b36ff7b9..121478331 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -8518,6 +8518,8 @@ meta_window_shortcuts_inhibited (MetaWindow         *window,
 gboolean
 meta_window_is_focusable (MetaWindow *window)
 {
+  g_return_val_if_fail (!window->unmanaging, FALSE);
+
   return META_WINDOW_GET_CLASS (window)->is_focusable (window);
 }