Fix Diffusion crash

Summary: This fixes a crash that happens when visiting Diffusion pages due to an undefined variable. $title is only defined if it has a status to show, but then it uses it anyway and fails.

Test Plan: Pages stopped crashing and people stopped complaining.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D8906