deregister_globals causes error when cookie called GLOBALS is set to scalar value

$cookie = &$_COOKIE;

while (isset($cookie['GLOBALS']))

{

  foreach ($cookie['GLOBALS'] as $registered_var => $value)

  {     

    if(!isset($not_unset[$registered_var]))                       

    {		

      unset($GLOBALS[$registered_var]);

    }

  }

  $cookie = &$cookie['GLOBALS'];

}               

setcookie('GLOBALS', 'TEST');

deregister_globals();