delete form after deleting survey

after deleting a survey, the unused form lives on in the database.
Here's a patch, to also delete the form

function survey_delete(&$node) {
  forms_delete($node->form);
  db_query("DELETE FROM {survey} WHERE nid=%d", $node->nid);
  //AND delete the form
  $form = forms_load(array('fid' => $node->nid));
  forms_delete($form);
}