[mutter] surface-actor-wayland: Handle stex being disposed

[Jonas Ådahl <jadahl src gnome org>]

commit a3c97ee53598d916267dc19e6f94eeb057a1e779
Author: Robert Mader <robert mader posteo de>
Date:   Sun Jun 30 15:03:32 2019 +0200

    surface-actor-wayland: Handle stex being disposed
    
    As the MetaShapedTexture might already got finalized, this can lead to a crash.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/755

 src/compositor/meta-surface-actor-wayland.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/src/compositor/meta-surface-actor-wayland.c b/src/compositor/meta-surface-actor-wayland.c
index 27c600c59..1c933d554 100644
--- a/src/compositor/meta-surface-actor-wayland.c
+++ b/src/compositor/meta-surface-actor-wayland.c
@@ -131,10 +131,12 @@ meta_surface_actor_wayland_dispose (GObject *object)
 {
   MetaSurfaceActorWayland *self = META_SURFACE_ACTOR_WAYLAND (object);
   MetaWaylandFrameCallback *cb, *next;
-  MetaShapedTexture *stex =
-    meta_surface_actor_get_texture (META_SURFACE_ACTOR (self));
+  MetaShapedTexture *stex;
+
+  stex = meta_surface_actor_get_texture (META_SURFACE_ACTOR (self));
+  if (stex)
+    meta_shaped_texture_set_texture (stex, NULL);
 
-  meta_shaped_texture_set_texture (stex, NULL);
   if (self->surface)
     {
       g_object_remove_weak_pointer (G_OBJECT (self->surface),