Fix SVN form_box error

Summary: Fixes T12915.

Test Plan: Test a SVN repository locally, ensure page loads.

Reviewers: epriestley

Subscribers: Korvin

Maniphest Tasks: T12915

Differential Revision: https://secure.phabricator.com/D18207

src/applications/diffusion/controller/DiffusionRepositoryController.php

@@ -371,7 +371,7 @@ final class DiffusionRepositoryController extends DiffusionController {
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
-    $locate_panel = null;
+    $form_box = null;
     if ($repository->canUsePathTree()) {
       Javelin::initBehavior(
         'diffusion-locate-file',