fix: cast fileid to string in getMountsForFileId

Signed-off-by: Robin Appelman <robin@icewind.nl>

Author: icewind1991

lib/private/Files/Config/UserMountCache.php

@@ -353,6 +353,7 @@ private function getCacheInfoFromFileId($fileId): array {
 	 * @since 9.0.0
 	 */
 	public function getMountsForFileId($fileId, $user = null) {
+		$fileId = (int)$fileId;
 		try {
 			[$storageId, $internalPath] = $this->getCacheInfoFromFileId($fileId);
 		} catch (NotFoundException $e) {