fixup! fix appconfig tests

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

lib/private/AppConfig.php

@@ -348,7 +348,7 @@ protected function loadConfigValues() {
 		$rows = $result->fetchAll();
 		foreach ($rows as $row) {
 			if (!isset($this->cache[$row['appid']])) {
-				$this->cache[$row['appid']] = [];
+				$this->cache[(string)$row['appid']] = [];
 			}
 
 			$this->cache[(string)$row['appid']][(string)$row['configkey']] = (string)$row['configvalue'];