Fix exception on /project/

Summary: I missed testing this case when re-doing the navigation.

Test Plan: Test /project/, don't see fatal. Test mobile menu, works as expected.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11868

src/applications/project/controller/PhabricatorProjectController.php

@@ -25,6 +25,7 @@ abstract class PhabricatorProjectController extends PhabricatorController {
 
     $viewer = $this->getViewer();
 
+    $id = null;
     if ($for_app) {
       if ($project) {
         $id = $project->getID();