Summary:
Depends on D20271. Ref T10333. When a column is empty but a board is grouped (by priority, owner, etc) render the headers properly.
When a column has headers, don't apply the "empty" style even if it has no cards. This style just makes some empty space so you can drag-and-drop more easily, but headers do the same thing.
Test Plan: {F6264611}
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T10333
Differential Revision: https://secure.phabricator.com/D20272
1bdf446a80