magento2 – Magento 2.3.1 gets the HTTP 500 error after installing the theme

[CentOS 7.6.1810 / Apache 2.4.6 / PHP 7.1.28 / Magento 2.3.1]

I have installed porto theme.But it is impossible to access the product page.
Content of error_log
[Thu Apr 25 18:10:10.335721 2019] [php7:error] [pid 31336] [client 122.20.150.30:60875] PHP unrecoverable error: Unrecovered error: Calling the getData () function on member in /var/www/html/app/design/frontend/Smartwave/porto/Magento_Catalog/templates/product/view/details.phtml:18nStack trace: n # 0 /var/www/html/vendor/magento/framework/View/TemplateEngine/Php.php(59): include () n # 1 / var / www / html / vendor / magento / framework / View / Element / Template.php (271): Magento Framework View TemplateEngine Php-> render (Object (Magento Catalog Block Product View Details), / var / www / html / a … # Array) n # 2 /var/www/html/vendor/magento/framework/View/Element/Template.php(301):Magento Framework View Element Template-> fetchView (& # 39; / var / www / html / a …) n # 3 /var/www/html/vendor/magento/framework/View/Element/AbstractBlock.php(668): Magento Framework View Element Template -> _ toHtml () n # 4 /var/www/html/vendor/magento/framework/View/Layout.php(557): Magento Framework Life w Element AbstractBlock-> toHtml () n # 5 / var / www /html/vendor/magento/framework/View/Layout.php(533): Magento Framework View Layout -> _ renderBlock (& ​​# 39; product.info.de … # 6 / var / www / html / generated in / var / www / html / app / design / front / Smartwave / porto / Magento_Catalog / templates / product / view / details .phtml on line 18, referring to:

Thank you.