fix: Also cleanup orphaned shares user cannot be found anymore

Signed-off-by: Julius Härtl <jus@bitgrid.net>

apps/files_sharing/lib/OrphanHelper.php

 
 namespace OCA\Files_Sharing;
 
+use OC\User\NoUserException;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\Files\IRootFolder;
 use OCP\IDBConnection;
 	}
 
 	public function isShareValid(string $owner, int $fileId): bool {
-		$userFolder = $this->rootFolder->getUserFolder($owner);
+		try {
+			$userFolder = $this->rootFolder->getUserFolder($owner);
+		} catch (NoUserException $e) {
+			return false;
+		}
 		$nodes = $userFolder->getById($fileId);
 		return count($nodes) > 0;
 	}