Phriction - make the check for project sub pages more fine-grained

Summary:
we were just checking if projects/ was in the URI before barfing. Use some more fun utility functions such that we only complain if there is no project.

Fixes T4071.

Test Plan: made a subpage under a project - success! tried to make a project wiki page where there was no project - successful failure! tried to make a project wiki sub page where there was no project - successful failure!

Reviewers: epriestley, chad

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T4071

Differential Revision: https://secure.phabricator.com/D7527

src/applications/phriction/controller/PhrictionEditController.php

@@ -51,9 +51,11 @@ final class PhrictionEditController
         $content = id(new PhrictionContent())->load($document->getContentID());
       } else {
         if (PhrictionDocument::isProjectSlug($slug)) {
-          $project = id(new PhabricatorProject())->loadOneWhere(
-            'phrictionSlug = %s',
-            PhrictionDocument::getProjectSlugIdentifier($slug));
+          $project = id(new PhabricatorProjectQuery())
+            ->setViewer($user)
+            ->withPhrictionSlugs(array(
+              PhrictionDocument::getProjectSlugIdentifier($slug)))
+            ->executeOne();
           if (!$project) {
             return new Aphront404Response();
           }