Extra guard condition.

Author: johnbillion

collectors/theme.php

@@ -103,6 +103,11 @@ public function tear_down() {
 	 */
 	public function action_get_position( $name ) {
 		$filter = current_filter();
+
+		if ( ! $filter ) {
+			return;
+		}
+
 		$trace = new QM_Backtrace( array(
 			'ignore_hook' => array(
 				$filter => true,