Fatal error: Uncaught TypeError: Argument 1 passed to Magento\Catalog\Model\ProductRepository::prepareSku() must be of the type string, null given, called in /var/www/magento/htdocs/app/code/Magento/Catalog/Model/ProductRepository.php on line 675 and defined in /var/www/magento/htdocs/app/code/Magento/Catalog/Model/ProductRepository.php:685 Stack trace: #0 /var/www/magento/htdocs/app/code/Magento/Catalog/Model/ProductRepository.php(675): Magento\Catalog\Model\ProductRepository->prepareSku(NULL) #1 /var/www/magento/htdocs/app/code/Magento/Catalog/Model/ProductRepository.php(308): Magento\Catalog\Model\ProductRepository->saveProductInLocalCache(Object(Magento\Catalog\Model\Product\Interceptor), '70f219631131d9b...') #2 /var/www/magento/htdocs/app/code/Magento/Catalog/Model/ProductRepository.php(273): Magento\Catalog\Model\ProductRepository->cacheProduct('70f219631131d9b...', Object(Magento\Catalog\Model\Product\Interceptor)) #3 /var/www/magento/htdocs/generated/code/Magento/Catalog/Model/ProductRepository/Interceptor.php(37 in /var/www/magento/htdocs/app/code/Magento/Catalog/Model/ProductRepository.php on line 685