Fix an issue where the "viewer" is not passed to Bulk Edit controls properly master
Summary: See PHI1442. If you have a bulk-editable datasource field with a composite datasource, it can currently fatal on the bulk edit workflow because the viewer is not passed correctly. The error looks something like this: > Argument 1 passed to PhabricatorDatasourceEngine::setViewer() must be an instance of PhabricatorUser, null given, called in /Users/epriestley/dev/core/lib/phabricator/src/applications/typeahead/datasource/PhabricatorTypeaheadCompositeDatasource.php on line 231 Test Plan: Configured a Maniphest custom field with a composite datasource, then tried a bulk edit. Things worked cleanly instead of fataling. Differential Revision: https://secure.phabricator.com/D20841