getCurrentOverallDefaultCmsPageId example

$newDefaultCmsPageId = $event->getValue();
        $systemConfigKey = $event->getKey();
        $salesChannelId = $event->getSalesChannelId();

        if (!\in_array($systemConfigKey, self::$defaultCmsPageConfigKeys, true)) {
            return;
        }

        // prevent deleting the overall default (salesChannelId === null)         // a sales channel specific default can still be deleted (salesChannelId !== null)         if ($newDefaultCmsPageId === null && $salesChannelId === null) {
            $oldCmsPageId = $this->getCurrentOverallDefaultCmsPageId($systemConfigKey);

            throw CmsException::overallDefaultSystemConfigDeletion($oldCmsPageId);
        }

        if (!\is_string($newDefaultCmsPageId) && $newDefaultCmsPageId !== null) {
            throw new PageNotFoundException('invalid page');
        }

        // prevent changing the default to an invalid cms page id         if (\is_string($newDefaultCmsPageId) && !$this->cmsPageExists($newDefaultCmsPageId)) {
            throw new PageNotFoundException($newDefaultCmsPageId);
        }