R1:cd8a9c603ead

fix Maniphest search for null-like values edge case

Summary: wishlist has priority value of 0 which was messing things up. also fix search text so we can search for "0".

Test Plan: searched for stuff, got results

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1878

Differential Revision: https://secure.phabricator.com/D3948