Как исправить ошибку со способом оплаты Opencart: 'Необходимо указать способ оплаты!'?

if (!isset($this->request->post['shipping_method'])) {
                $json['error']['warning'] = $this->language->get('error_shipping');
            } else {
                $shipping = explode('.', $this->request->post['shipping_method']);

                if (!isset($shipping[0]) || !isset($shipping[1]) || !isset($this->session->data['shipping_methods'][$shipping[0]]['quote'][$shipping[1]])) {
                    $json['error']['warning'] = $this->language->get('error_shipping');
                }
            }

            if (!isset($this->request->post['payment_method'])) {
                $json['error']['warning'] = $this->language->get('error_payment');
            } elseif (!isset($this->session->data['payment_methods'][$this->request->post['payment_method']])) {
                $json['error']['warning'] = $this->language->get('error_payment');
            }

            if ($this->config->get('config_checkout_id')) {
                $this->load->model('catalog/information');

                $information_info = $this->model_catalog_information->getInformation($this->config->get('config_checkout_id'));

                if ($information_info && !isset($this->request->post['agree'])) {
                    $json['error']['warning'] = sprintf($this->language->get('error_agree'), $information_info['title']);
                }
            }