کرش کردن صفحه چک آوت

با سلام
از وقتی افزونه رو بروز کردم در صفحه چک آوت صفحه سفید با پیام دیباگ یا بعضی مواقع یه صفحه بسیار کوچک بهم ریخته مواجه میشم
دیباگینگ رو فعال کردم و خطای زیر رو میده

Fatal error: Uncaught TypeError: Return value of WC_Custom_Method::calculate_shipping() must be of the type boolean, none returned in /home/sitename/public_html/wp-content/plugins/persian-woocommerce-shipping/methods/pws-sefareshi-method.php:151 Stack trace: #0 /home/sitename/public_html/wp-content/plugins/woocommerce/includes/abstracts/abstract-wc-shipping-method.php(233): WC_Custom_Method->calculate_shipping(Array) #1 /home/sitename/public_html/wp-content/plugins/woocommerce/includes/class-wc-shipping.php(345): WC_Shipping_Method->get_rates_for_package(Array) #2 /home/sitename/public_html/wp-content/plugins/woocommerce/includes/class-wc-shipping.php(260): WC_Shipping->calculate_shipping_for_package(Array, 0) #3 /home/sitename/public_html/wp-content/plugins/woocommerce/includes/class-wc-cart.php(1391): WC_Shipping->calculate_shipping(Array) #4 /home/sitename/public_html/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(339): WC_Cart->calculate_shipping() #5 /home/sitename/public_html/wp-content/plugins/woo in /home/sitename/public_html/wp-content/plugins/persian-woocommerce-shipping/methods/pws-sefareshi-method.php on line 151