Can't undo changes using reject changes button in form with button to approve pending changes. Normally, it should bring to page with summary what will be undone and prompt for edit summary. Instead, it shows error message review_reject_nulledits. Edits are not blank. Only applicable when there is only one pending edit; otherwise the edit summary used is broken but the revert is still possible
It affects all wikis with pending changes with form to flag revision or undo using button "reject".