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

src/applications/differential/herald/DifferentialReviewersHeraldAction.php

@@ -57,7 +57,7 @@ abstract class DifferentialReviewersHeraldAction
       // If we're applying a stronger status (usually, upgrading a reviewer
       // into a blocking reviewer), skip this check so we apply the change.
       $old_strength = DifferentialReviewerStatus::getStatusStrength(
-        $reviewers[$phid]->getStatus());
+        $reviewers[$phid]->getReviewerStatus());
       if ($old_strength <= $new_strength) {
         continue;
       }