Fatal error when previewing email template

In Woocommerce>Settings>Emails, when I click “Click here to preview email template,” I get the following error: “Fatal error: Call to a member function get_cart() on a non-object in /wp-content/plugins/woocommerce-quick-donation/woocommerce-quick-donation.php on line 97”

https://ww.wp.xz.cn/plugins/woocommerce-quick-donation/