Add status to PhabricatorProjectQuery->getPagingValueMap()

Summary: Probably fixes https://discourse.phabricator-community.org/t/unhandled-exception-for-certain-fields-in-maniphest-search/2263. Couldn't repro this locally, but this is almost certainly the correct fix.

Test Plan: doitlive

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D19951