Fix an issue with rendering PHID lists containing null in Maniphest

Summary: See IRC. Someone got a `null` in CCPHIDs somehow. Moving to subscriptions should prevent this, but paper over it for now.

Test Plan: Will have @dctrwatson check.

Reviewers: btrahan, dctrwatson

Reviewed By: btrahan

CC: dctrwatson, aran

Differential Revision: https://secure.phabricator.com/D7330

src/applications/base/controller/PhabricatorController.php

@@ -319,7 +319,7 @@ abstract class PhabricatorController extends AphrontController {
 
     return implode_selected_handle_links($style_map[$style],
       $this->getLoadedHandles(),
-      $phids);
+      array_filter($phids));
   }
 
   protected function buildApplicationMenu() {