Fix insufficient loading for processing Differential mail

Summary: Some actions (notably, `!accept`) require more information than we currently load.

Test Plan: Piped in some `!accept` mail using `bin/mail receive-test`.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D8844

src/applications/differential/mail/DifferentialRevisionMailReceiver.php

@@ -15,13 +15,13 @@ final class DifferentialRevisionMailReceiver
   protected function loadObject($pattern, PhabricatorUser $viewer) {
     $id = (int)trim($pattern, 'D');
 
-    $results = id(new DifferentialRevisionQuery())
+    return id(new DifferentialRevisionQuery())
       ->setViewer($viewer)
       ->withIDs(array($id))
       ->needReviewerStatus(true)
-      ->execute();
+      ->needReviewerAuthority(true)
-
+      ->needActiveDiffs(true)
-    return head($results);
+      ->executeOne();
   }
 
   protected function processReceivedObjectMail(