Fix Main Directory Jump Nav CSS leak

Summary: Good that this isn't a water leak. Else I'd be screwed.

Test Plan:
Visited Main Dir. Looks normal.

Visited Maniphest. Saw ominous shadow on top for saved query. Saw normal paddings for populated list filters.

Reviewers: epriestley, chad

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5536