Fix default parameter of OC_DB::executeAudited()

* fixes #7546

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

lib/private/legacy/db.php

@@ -105,11 +105,11 @@ class OC_DB {
 	 * @param mixed $stmt OC_DB_StatementWrapper,
 	 *					  an array with 'sql' and optionally 'limit' and 'offset' keys
 	 *					.. or a simple sql query string
-	 * @param array|null $parameters
+	 * @param array $parameters
 	 * @return OC_DB_StatementWrapper
 	 * @throws \OC\DatabaseException
 	 */
-	static public function executeAudited( $stmt, array $parameters = null) {
+	static public function executeAudited( $stmt, array $parameters = []) {
 		if (is_string($stmt)) {
 			// convert to an array with 'sql'
 			if (stripos($stmt, 'LIMIT') !== false) { //OFFSET requires LIMIT, so we only need to check for LIMIT