Clicking the search icon in empty search field should link to advanced search

Summary: Fixes T6664, clicking search icon in empty search field should link to advanced search

Test Plan: navigate to home page, click search icon or click into search box and hit enter. Advanced search page should open.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6664

Differential Revision: https://secure.phabricator.com/D10947