/**
  * Redirect to a specific page
  *
  * @param Mage_Adminhtml_Controller_Action $controller
  */
 protected function _redirect($controller, $url = null)
 {
     $controller->setFlag('', Mage_Core_Controller_Varien_Action::FLAG_NO_DISPATCH, true);
     if (null === $url) {
         $url = Mage::getSingleton('adminhtml/url')->getUrl('*/*/denied');
     } elseif (is_array($url)) {
         $url = Mage::getSingleton('adminhtml/url')->getUrl(array_shift($url), $url);
     } elseif (false === strpos($url, 'http', 0)) {
         $url = Mage::getSingleton('adminhtml/url')->getUrl($url);
     }
     Mage::app()->getResponse()->setRedirect($url);
 }