Fix Phriction toc rendering when toc is null

Summary: Removes the exception, maybe there is a better way, but landing this for now. Fixes T9829

Test Plan: Test pages with and without a table of contents

Reviewers: epriestley, avivey

Subscribers: epriestley

Maniphest Tasks: T9829

Differential Revision: https://secure.phabricator.com/D14546

src/applications/phriction/storage/PhrictionContent.php

@@ -115,9 +115,6 @@ final class PhrictionContent extends PhrictionDAO
    * @task markup
    */
   public function getRenderedTableOfContents() {
-    if ($this->renderedTableOfContents === null) {
-      throw new PhutilInvalidStateException('didMarkupText');
-    }
     return $this->renderedTableOfContents;
   }