fixup! Take 1 on preview delete job

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

Author: rullzer

lib/private/Preview/BackgroundCleanupJob.php

@@ -86,7 +86,8 @@ private function getOldPreviewLocations(): \Iterator {
 		$qb->selectDistinct('a.name')
 			->from('filecache', 'a')
 			->leftJoin('a', 'filecache', 'b', $qb->expr()->eq(
-				$qb->expr()->castColumn('a.name', IQueryBuilder::PARAM_INT), 'b.fileid'
+				$qb->expr()->castColumn('a.name', IQueryBuilder::PARAM_INT),
+				$qb->expr()->castColumn('b.fileid', IQueryBuilder::PARAM_INT)
 			))
 			->leftJoin('a', 'filecache', 'c', $qb->expr()->eq(
 				'a.fileid', 'c.parent'