Neos\Media\Browser\Controller\Module\Management\AssetController::deleteAssetCollectionAction PHP Метод

    public function deleteAssetCollectionAction(AssetCollection $assetCollection)
    {
        foreach ($this->siteRepository->findByAssetCollection($assetCollection) as $site) {
            $site->setAssetCollection(null);
            $this->siteRepository->update($site);
        }
        parent::deleteAssetCollectionAction($assetCollection);
    }