Undefined index errors when WP_DEBUG = true

In admin area:

Notice: Undefined index: token in /var/www/html/wp-content/plugins/woocommerce-gateway-brainblocks/woocommerce-gateway-brainblocks.php on line 326
Notice: Undefined index: wc_order_id in /var/www/html/wp-content/plugins/woocommerce-gateway-brainblocks/woocommerce-gateway-brainblocks.php on line 327
Notice: Undefined index: token in /var/www/html/wp-content/plugins/woocommerce-gateway-brainblocks/woocommerce-gateway-brainblocks.php on line 326
Notice: Undefined index: wc_order_id in /var/www/html/wp-content/plugins/woocommerce-gateway-brainblocks/woocommerce-gateway-brainblocks.php on line 327

And similar area is thrown in checkout (maybe only if WP_DEBUG = true)