R1:e1ee8ba428e4

Fix a bad getStatus() call which is fataling during Herald rule evaluation

Summary: Hit this while `arc diff`'ing something which is triggering 2+ rules which add reviewers, I think.

Test Plan: Dug this out of a production stack trace; will push and `arc diff` again.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D17534