Override handler for views_ui_edit_display_form
function views_ui_config_item_form_build_group($form, &$form_state) {
$item =& $form_state['handler']->options;
// flip. If the filter was a group, set back to a standard filter.
$item['is_grouped'] = empty($item['is_grouped']);
// If necessary, set new defaults:
if ($item['is_grouped']) {
$form_state['handler']
->build_group_options();
}
$form_state['view']
->get('executable')
->setItem($form_state['display_id'], $form_state['type'], $form_state['id'], $item);
$form_state['view']
->addFormToStack($form_state['form_key'], $form_state['display_id'], array(
$form_state['type'],
$form_state['id'],
), TRUE, TRUE);
views_ui_cache_set($form_state['view']);
$form_state['rerender'] = TRUE;
$form_state['rebuild'] = TRUE;
$form_state['force_build_group_options'] = TRUE;
}