wayland: Do not check the pointer focus when receiving wl_pointer.frame

The frame event is also meant to compress wl_pointer.leave events, at this
point the focus surface will be definitely NULL. In the end, wl_pointer.frame
should flush the last composed event despite the pointer focus.

https://bugzilla.gnome.org/show_bug.cgi?id=765065

gdk/wayland/gdkdevice-wayland.c

@@ -1467,9 +1467,6 @@ pointer_handle_frame (void              *data,
 {
   GdkWaylandSeat *seat = data;
 
-  if (!seat->pointer_info.focus)
-    return;
-
   GDK_NOTE (EVENTS,
             g_message ("frame, seat %p", seat));