Set a property so that unit tests run on PHP7

Summary: Without this change PHP throws because idx() is passed null as the property is not intialzied

Test Plan: arc unit --everything

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D14345

src/aphront/AphrontRequest.php

@@ -28,7 +28,7 @@ final class AphrontRequest extends Phobject {
   private $applicationConfiguration;
   private $site;
   private $controller;
-  private $uriData;
+  private $uriData = array();
   private $cookiePrefix;
 
   public function __construct($host, $path) {