Elasticsearch: add "engines" virtual function to avoid error

adminer/drivers/elastic.inc.php

@@ -205,6 +205,10 @@ if (isset($_GET["elastic"])) {
 	function db_collation($db, $collations) {
 	}
 	
+	function engines() {
+		return array();
+	}
+
 	function count_tables($databases) {
 		global $connection;
 		$return = $connection->query('_mapping');