Merge pull request #5243 from nextcloud/backport/5227/stable18

[stable18] Fix uninitialised variable

developer_manual/app/storage/database.rst

@@ -102,7 +102,7 @@ To create a mapper, inherit from the mapper base class and call the parent const
                ->setMaxResults($limit)
                ->setFirstResult($offset);
 
-            return $this->findEntities($sql);
+            return $this->findEntities($qb);
         }