[fw-mvc] create custom default route

All,

I've created a custom default route:

<?php
class My_Controller_Router_Route_Invalid implements
Zend_Controller_Router_Route_Interface
{
public $defaults = array(
'module' => 'default',
'controller' => 'error',
'action' => 'error',
);

public function match($path)
{
return $this->defaults;
}

public function assemble($data = array())
{
return '';
}

public static function getInstance(Zend_Config $config)
{
return new self();
}
}

And added it as such:
$router = $front->getRouter();
//$router->addRoute('default', new
My_Controller_Router_Route_Invalid());
$routesConfig = new Zend_Config_Ini('routes.ini');
$router->addConfig($routesConfig);

But it just doesn't work, it gives a blank page when i go to any url
after this, any clue what's wrong?

thanks!

Yi