Error when add new users about admin HOT 2 OPEN

    //$this->data['User']['password'] = AuthComponent::password($this->data['User']['password']);
    $this->data['User']['password'] = md5($this->data['User']['password']);

    return true;
}

public $belongsTo = array('Group');

// public $actsAs = array('Acl' => array('type' => 'requester'));

public function parentNode() {
    if (!$this->id && empty($this->data)) {
        return null;
    }
    if (isset($this->data['User']['group_id'])) {
        $groupId = $this->data['User']['group_id'];
    } else {
        $groupId = $this->field('group_id');
    }
    if (!$groupId) {
        return null;
    } else {
        return array('Group' => array('id' => $groupId));
    }
}