wayland/surface: Ensure to apply cached state

It is possible that we never create a cached state for a surface
even if it is synced. That is the case if `commit()` is never called.
We still need to call `apply_state()` in this case in order to run
e.g. `role_post_apply_state()` or `parent_state_applied` on subsurfaces.

So just ensure to initialize the cached state instead of bailing out.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2232>

src/wayland/meta-wayland-surface.c

@@ -969,9 +969,7 @@ cleanup:
 void
 meta_wayland_surface_apply_cached_state (MetaWaylandSurface *surface)
 {
-  if (!surface->cached_state)
-    return;
-
+  meta_wayland_surface_ensure_cached_state (surface);
   meta_wayland_surface_apply_state (surface, surface->cached_state);
 }