wayland: don't send notify when window is being unmanaged

If we try to send notify event (either from surface_state_changed()
or from meta_window_wayland_move_resize_internal()),
we will crash, because we don't have a sufrace anymore.
There's no reason why to resize the window that is being
unmanaged anyway.

https://bugzilla.gnome.org/show_bug.cgi?id=751847

src/core/window.c

@@ -1259,6 +1259,7 @@ meta_window_unmanage (MetaWindow  *window,
   GList *tmp;
 
   meta_verbose ("Unmanaging %s\n", window->desc);
+  window->unmanaging = TRUE;
 
 #ifdef HAVE_WAYLAND
   /* This needs to happen for both Wayland and XWayland clients,
@@ -1286,8 +1287,6 @@ meta_window_unmanage (MetaWindow  *window,
 
   meta_display_unregister_stamp (window->display, window->stamp);
 
-  window->unmanaging = TRUE;
-
   if (meta_prefs_get_attach_modal_dialogs ())
     {
       GList *attached_children = NULL, *iter;

src/wayland/meta-window-wayland.c

@@ -124,6 +124,10 @@ surface_state_changed (MetaWindow *window)
 {
   MetaWindowWayland *wl_window = META_WINDOW_WAYLAND (window);
 
+  /* don't send notify when the window is being unmanaged */
+  if (window->unmanaging)
+    return;
+
   meta_wayland_surface_configure_notify (window->surface,
                                          wl_window->last_sent_width,
                                          wl_window->last_sent_height,
@@ -166,6 +170,10 @@ meta_window_wayland_move_resize_internal (MetaWindow                *window,
 
   g_assert (window->frame == NULL);
 
+  /* don't do anything if we're dropping the window, see #751847 */
+  if (window->unmanaging)
+    return;
+
   /* The scale the window is drawn in might change depending on what monitor it
    * is mainly on. Scale the configured rectangle to be in logical pixel
    * coordinate space so that we can have a scale independent size to pass
@@ -396,12 +404,6 @@ appears_focused_changed (GObject    *object,
                          gpointer    user_data)
 {
   MetaWindow *window = META_WINDOW (object);
-
-  /* When we're unmanaging, we remove focus from the window,
-   * causing this to fire. Don't do anything in that case. */
-  if (window->unmanaging)
-    return;
-
   surface_state_changed (window);
 }