Fix fatal when looking at an unknown-config error.

Summary:
Going to /config/issue/config.unknown.phabricator.setup/ fataled with

  Call to a member function getLocked() on a non-object

Test Plan: Went to /config/issue/config.unknown.phabricator.setup/ and saw the page render.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4633

src/applications/config/view/PhabricatorSetupIssueView.php

@@ -169,7 +169,7 @@ final class PhabricatorSetupIssueView extends AphrontView {
     } else {
       $update = array();
       foreach ($configs as $config) {
-        if ($options[$config]->getLocked()) {
+        if (!idx($options, $config) || $options[$config]->getLocked()) {
           continue;
         }
         $link = phutil_render_tag(