public function handle(GetResponseEvent $event)
    {
        $request = $event->getRequest();

        $response = $this->successHandler->onLogoutSuccess($request);
        if (!$response instanceof Response) {
            throw new \RuntimeException('Logout Success Handler did not return a Response.');
        }

        // handle multiple logout attempts gracefully
        if (null !== $token = $this->securityContext->getToken()) {
            foreach ($this->handlers as $handler) {
                $handler->logout($request, $response, $token);
            }
        }

        $this->securityContext->setToken(null);
        $event->setResponse($response);
    }