Fix 'stripos(): Non-string needles will be interpreted as strings in …

…the future'

tests/lib/Util/User/MemoryAccountMapper.php

@@ -76,7 +76,7 @@ public function search($fieldName, $pattern, $limit, $offset) {
 			return self::$accounts;
 		}
 		$match = \array_filter(self::$accounts, function (Account $a) use ($pattern) {
-			return \stripos($a->getUserId(), $pattern);
+			return \stripos($a->getUserId(), (string) $pattern);
 		});
 
 		return $match;