[ingo] problem using maildrop as script

[carlos maca]

when i active the script as "maildrop" in backends.php, a messages appears
when i enter in filter : "*Notice*: Undefined index: path_style in *
/home/webmaster/www/horde/ingo/lib/Script/maildrop.php* on line *501"
this is the copy of my maildrop.php script on line 501:  *
  function maildropPath($folder)
    {
        /* NOTE: '$DEFAULT' here is a literal, not a PHP variable. */
        if (isset($this->_params) &&
            ($this->_params['path_style'] == 'maildir')) {
--------------------------> Line 501
            if (empty($folder) || ($folder == 'INBOX')) {
                return 'to "${DEFAULT}';
            }
            if (substr($folder, 0, 6) == 'INBOX.') {
                $folder = substr($folder, 6);
            }
            return '"${DEFAULT}/.' . $folder . '/"';
        } else {
            if (empty($folder) || ($folder == 'INBOX')) {
                return 'to ${DEFAULT}';
            }
            return str_replace(' ', '\ ', $folder);
        }
    }

}

The same error appears when i try to activate the Script.
Any helps, will be very welcome. Carlos.
* *