R1:ea8be11addd7

Fix a qsprintf() issue in mail queries

Summary: Ref T920. Bumped into this while looking at SMS support.

Test Plan: Loaded `/mail/`, no more `qsprintf()` warning.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T920

Differential Revision: https://secure.phabricator.com/D19936