Silverstripe: отношение-член много-много-ноль, формирует внешний интерфейс

Неустранимая ошибка: вызов функции-члена Services () при нулевом значении

class MemberProfileViewer extends Page_Controller {

    // ...

    public function Servizi() {
        $source = null;
        if ($id = (int)$this->urlParams['ID']) {
            $member = Member::get()->byID($id);
            if ($member instanceof Member) {
                return $source = $member->Services()->map('Title','Title');
            }
        } 

        if (is_null($id)) {
            return $this->redirect('/');
        }

        if (is_null($source)) {
            return $this->httpError(404);
        } 

    }

    public function form() {

        $fields = new FieldList(
            CheckboxSetField::create(
                $name = "ServiceID",
                $title = "Select",
                $source = $this->Servizi()
            ),
        )

        $actions = FieldList::create(
                FormAction::create('form', 'Send')
                    ->setUseButtonTag(true)
                    ->addExtraClass('btn btn-primary')
        );

        $validator = new RequiredFields('ServiceID');

        $form = new Form($this, 'form', $fields, $actions, $validator);
        $form->setFormMethod('POST', true);
        return $form;
    }

    public function doform($data, $form) {
        $form->sessionMessage(
            "Thank you, you will be contacted as soon as possible by our consultant.", 'good'
        );

        $submission = new RequestForm();
        $form->saveInto($submission);
        $submission->write();

        return $this->redirectBack();

    }

}

всегда равно нулю
Я не знаю, как решить

Да, проблема решена!

class MemberProfileViewer extends Page_Controller {

    // ...

    public function currentPageID() {
        $id = 0;
        $request = $this->getRequest();
        if(is_numeric($request->requestVar('ID')))  {
            $id = $request->requestVar('ID');
        } elseif (is_numeric($request->param('ID'))) {
            $id = $request->param('ID');
        }

        $id = (int)$id;
        return $id;
    }

    public function Servizi() {
        $source = null;
        if ($id = $this->currentPageID()) {
            Session::set('ID', $id);
            return $source = Member::get()->byID($id)->Services()->map('Title','Title')->toArray();
        } elseif (is_null($source)) {
           return $source = Member::get()->byID(Session::get('ID'))->Services()->map('Title','Title')->toArray();
        } 

    }

    public function form() {

        $fields = new FieldList(
            CheckboxSetField::create(
                $name = "Service",
                $title = "Select",
                $source = $this->Servizi()
            ),
        )

        $actions = FieldList::create(
                FormAction::create('form', 'Send')
                    ->setUseButtonTag(true)
                    ->addExtraClass('btn btn-primary')
        );

        $validator = new RequiredFields('Service');

        $form = new Form($this, 'form', $fields, $actions, $validator);
        $form->setFormMethod('POST', true);

        $data = Session::get("FormData.{$form->getName()}.data");
        return $data ? $form->loadDataFrom($data) : $form;
    }

    public function doform($data, $form) {
        Session::set("FormData.{$form->getName()}.data", $data);

        $submission = new RequestForm();
        $form->saveInto($submission);
        $submission->write();

        $form->sessionMessage(
            "Thank you, you will be contacted as soon as possible by our consultant.", 'good'
        );

        Session::clear("FormData.{$form->getName()}.data");
        return $this->redirectBack();

    }

}