Fehler in Gutschein /contao?do=event_coupon

Kernel->handle(object(Request))in public/index.php (line 44)

1. $loader = require __DIR__.'/../vendor/autoload.php';
3. $request = Request::createFromGlobals();
4. $kernel = ContaoKernel::fromRequest(dirname(__DIR__), $request);
6. $response = $kernel->handle($request);
7. $response->send();
9. if ($kernel instanceof TerminableInterface) {
10.     $kernel->terminate($request, $response);
11. }

ErrorException: Warning: Undefined variable $simple_products at vendor/fast-media/contao-coupons/dca/tl_coupon.php:324 at include('/www/htdocs/w01de797/contao/vendor/fast-media/contao-coupons/dca/tl_coupon.php') (vendor/contao/core-bundle/src/Resources/contao/library/Contao/DcaLoader.php:120) at Contao\DcaLoader->loadDcaFiles(false) (vendor/contao/core-bundle/src/Resources/contao/library/Contao/DcaLoader.php:75) at Contao\DcaLoader->load() (vendor/contao/core-bundle/src/Resources/contao/library/Contao/Controller.php:1448) at Contao\Controller::loadDataContainer('tl_coupon') (vendor/contao/core-bundle/src/Resources/contao/classes/Backend.php:387) at Contao\Backend->getBackendModule('event_coupon', null) (vendor/contao/core-bundle/src/Resources/contao/controllers/BackendMain.php:168) at Contao\BackendMain->run() (vendor/contao/core-bundle/src/Controller/BackendController.php:49) at Contao\CoreBundle\Controller\BackendController->mainAction() (vendor/symfony/http-kernel/HttpKernel.php:163) at Symfony\Component\HttpKernel\HttpKernel->handleRaw(object(Request), 1) (vendor/symfony/http-kernel/HttpKernel.php:75) at Symfony\Component\HttpKernel\HttpKernel->handle(object(Request), 1, true) (vendor/symfony/http-kernel/Kernel.php:202) at Symfony\Component\HttpKernel\Kernel->handle(object(Request)) (public/index.php:44)