Error when running plugin with PHP 8.1

Hi!

I’m trying to upgrade my site to PHP 8.1, and I’m getting this error from your plugin:

Backtrace from fatal error ‘Optional parameter $amount declared before required parameter $currency is implicitly treated as a required parameter’ at /var/www/html/wp-content/plugins/zipmoney-payments-woocommerce/includes/api/class-wc-zipmoney-payment-gateway-api-charge.php 36

Could you please change this line from:

public function refund_order_charge( WC_Order $order, $api_key, $amount = 0, $currency, $reason = '' ) {

to:

public function refund_order_charge( WC_Order $order, $api_key, $amount, $currency, $reason = '' ) {