Steps to Reproduce:
- Have more than 100 tasks which you have flagged
- Navigate to https://phabricator.wikimedia.org/flag/
- Given that you have had many flagged tasks, click Next at the bottom.
- Can be reproduced with an arbitrary ?after=### request parameter.
- You get the following error:
Call to undefined method PhabricatorFlagQuery::withIDs()
- The next page shows.