xwm: check for a buffer before mapping

xwayland/xwm.c

@@ -885,8 +885,10 @@ static void read_surface_property(struct wlr_xwm *xwm,
 
 static void xwayland_surface_handle_commit(struct wl_listener *listener, void *data) {
 	struct wlr_xwayland_surface *xsurface = wl_container_of(listener, xsurface, surface_commit);
+	if (wlr_surface_has_buffer(xsurface->surface)) {
 		wlr_surface_map(xsurface->surface);
 	}
+}
 
 static void xwayland_surface_handle_map(struct wl_listener *listener, void *data) {
 	struct wlr_xwayland_surface *xsurface = wl_container_of(listener, xsurface, surface_map);