aMember (site.php): User friendly error message display in case of there is no product to purchase

site.php

<?php

Am_Di::getInstance()->hook->add(Am_Event::AFTER_RENDER, function(Am_Event_AfterRender $e) {
   if (defined('AM_ADMIN') && AM_ADMIN) return;
   if (
       stripos($e->getOutput(), 'There are no products available for purchase. Please come back later') !== false
       && $e->getDi()->request->getControllerName() == 'signup'
   ) {
       $url = $e->getDi()->url('no-product', ['c' => $e->getDi()->request->getParam('c')], false);
       header("Location: {$url}");
       exit;
   }
});

class NoProductController extends Am_Mvc_Controller
{
    function indexAction()
    {
        $r = $this->loadForm();

        if ($_ = $this->getDi()->navigationUser->findOneById('add-renew-' . ($this->getFiltered('c') ?: 'default'))) {
            $_->setActive(true);
        }

        $v = $this->view;
        $v->title = $r->title;
        $v->content = <<<CUT
<div style="color:red">There are no products available for purchase. Please come back later</div>
CUT;
        $v->display('member/layout.phtml');
    }

    function loadForm()
    {
        if ($c = $this->getFiltered('c')) {
            $record = $this->getDi()->savedFormTable->findFirstBy(['code' => $c, 'type' => SavedForm::T_SIGNUP]);
        } else {
            $record = $this->getDi()->savedFormTable->getDefault($this->getDi()->auth->getUserId() ? SavedForm::D_MEMBER : SavedForm::D_SIGNUP);
        }

        $record = $this->getDi()->hook->filter($record, Am_Event::LOAD_SIGNUP_FORM, [
            'request' => $this->getRequest(),
            'user' => $this->getDi()->auth->getUser(),
        ]);

        return $record;
    }
}