Don't include resigned reviewers in the Differential "To" list

Summary: Ref T12689. See PHI178. This isn't a complete solution (you may still get mailed via packages/projects) but should fix the obvious issue, where "Resigned" reviewers are incorrectly always sent mail directly.

Test Plan: Had Alice resign, interacted as Bailey, no mail to Alice.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T12689

Differential Revision: https://secure.phabricator.com/D18758

Author: epriestley

src/applications/differential/editor/DifferentialTransactionEditor.php

@@ -630,6 +630,10 @@ protected function getMailTo(PhabricatorLiskDAO $object) {
     $phids = array();
     $phids[] = $object->getAuthorPHID();
     foreach ($object->getReviewers() as $reviewer) {
+      if ($reviewer->isResigned()) {
+        continue;
+      }
+
       $phids[] = $reviewer->getReviewerPHID();
     }
     return $phids;