TileMap: _update_dirty_quadrants() cancel pending update pre return

(cherry picked from commit 5b3acd287dcc08e6a05f7526f3bd28c5a00d8075)

scene/2d/tile_map.cpp

@@ -268,10 +268,10 @@ void TileMap::_update_dirty_quadrants() {
 
 	if (!pending_update)
 		return;
-	if (!is_inside_tree())
-		return;
-	if (!tile_set.is_valid())
+	if (!is_inside_tree() || !tile_set.is_valid()) {
+		pending_update = false;
 		return;
+	}
 
 	VisualServer *vs = VisualServer::get_singleton();
 	Physics2DServer *ps = Physics2DServer::get_singleton();