Fix Asana sync for users with no profile image

Summary: Ref T2852. We don't get a result back here if there's no photo.

Test Plan: Resynch'd an account with no photo.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2852

Differential Revision: https://secure.phabricator.com/D6480