code: protected function createAction($action, $page)
      {
          if (($action === '') || ($action === false)) {
              return $page->expandUrl($page->getUrl());
          }
  
          return $page->expandUrl(new SimpleUrl($action));
      }
docs: Combined action attribute with current location to get an absolute form target.
  
  @param string $action    Action attribute from form tag.
  @param $page   Page location.
  
  @return SimpleUrl        Absolute form target.