after the last update this message showed up

Warning: Undefined array key 1 in?/home/u320651781/domains/rosettafragrance.com/public_html/wp-content/plugins/product-subtitle-for-woocommerce/includes/public/class-pswc-shop.php?on line?36

Hi, How i can disable to show the subtitle on the emails? I have activated only single product page, i am not sure why is going at the same time on the order email. Thank you,