Index: src/applications/herald/adapter/HeraldDifferentialRevisionAdapter.php
===================================================================
--- src/applications/herald/adapter/HeraldDifferentialRevisionAdapter.php
+++ src/applications/herald/adapter/HeraldDifferentialRevisionAdapter.php
@@ -353,7 +353,7 @@
       case self::FIELD_REPOSITORY_PROJECTS:
         $repository = $this->loadRepository();
         if (!$repository) {
-          return null;
+          return array();
         }
         return $repository->getProjectPHIDs();
       case self::FIELD_DIFF_CONTENT: