[mutter] wayland/subsurface: Handle clients committing on destroyed subsurface

[Jonas Ådahl <jadahl src gnome org>]

commit 704bd4c33129ea50b14493d6cbd6aca4db827f36
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Apr 17 13:27:35 2017 +0800

    wayland/subsurface: Handle clients committing on destroyed subsurface
    
    A client can still commit state to a destroyed subsurface. It wont
    update anything on the screen, since the subsurface will not be
    visible, but mutter should still handle it and not crash.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=781391

 src/wayland/meta-wayland-surface.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/wayland/meta-wayland-surface.c b/src/wayland/meta-wayland-surface.c
index 3323742..5a0e0ee 100644
--- a/src/wayland/meta-wayland-surface.c
+++ b/src/wayland/meta-wayland-surface.c
@@ -615,7 +615,7 @@ subsurface_role_get_toplevel (MetaWaylandSurfaceRole *surface_role)
     meta_wayland_surface_role_get_surface (surface_role);
   MetaWaylandSurface *parent = surface->sub.parent;
 
-  if (parent->role)
+  if (parent && parent->role)
     return meta_wayland_surface_role_get_toplevel (parent->role);
   else
     return NULL;