fix(files_external): set size to -1 for root entry

This allows the system to recogise that the mount has not been scanned
and do it when necessary.

Signed-off-by: Salvatore Martire <4652631+salmart-dev@users.noreply.github.com>

Author: salmart-dev

apps/files_external/lib/Service/MountCacheService.php

@@ -119,7 +119,7 @@ private function getCacheEntryForRoot(IUser $user, StorageConfig $storage): ICac
 		$data = [
 			'path' => '',
 			'path_hash' => md5(''),
-			'size' => 0,
+			'size' => -1,
 			'unencrypted_size' => 0,
 			'mtime' => 0,
 			'mimetype' => ICacheEntry::DIRECTORY_MIMETYPE,