If account.editable is set to false, we try to add a null button and fatal:
Argument 1 passed to PHUIHeaderView::addActionLink() must be an instance of PHUIButtonView, null given, called in /srv/phabricator/phabricator/src/applications/settings/panel/PhabricatorSettingsPanel.php on line 290
Instead, don't try to render null as a button.