Convert AphrontErrorView to safe HTML

Summary: Done by searching for `AphrontErrorView` and then `appendChild()`.

Test Plan:
Looked at Commit Detail.
Looked at Revision Detail.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2432

Differential Revision: https://secure.phabricator.com/D4843

src/applications/fact/controller/PhabricatorFactHomeController.php

@@ -94,9 +94,10 @@ final class PhabricatorFactHomeController extends PhabricatorFactController {
       return id(new AphrontErrorView())
         ->setSeverity(AphrontErrorView::SEVERITY_NOTICE)
         ->setTitle(pht('No Chartable Facts'))
-        ->appendChild(
-          '<p>'.pht(
-            'There are no facts that can be plotted yet.').'</p>');
+        ->appendChild(phutil_tag(
+          'p',
+          array(),
+          pht('There are no facts that can be plotted yet.')));
     }
 
     $form = id(new AphrontFormView())