R1:9383abc6b07c

Remove unnecessary empty checks from willFilterPage()

Summary: Fixes T3600. These checks are obsolete after D6512.

Test Plan: Syntax / static / inspection.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T3600

Differential Revision: https://secure.phabricator.com/D6563