broken plugin with version WP 3.6

Warning: session_start() [function.session-start]: Cannot send session cache limiter – headers already sent (output started at /mnt/web-data1/pomponella_cz/public_html/www/wp-content/plugins/woocommerce-add-extra-charges-option-to-payment-gateways/woocommerce-add-extra-charges-option-to-payment-gateways.php:1) in /mnt/web-data1/pomponella_cz/public_html/www/wp-content/plugins/yith-woocommerce-wishlist/class.yith-wcwl.php on line 54

http://wordpress.org/plugins/woocommerce-add-extra-charges-option-to-payment-gateways/