wc_customer_order_csv_export_order_row.php

<?php
add_filter('wc_customer_order_csv_export_order_row','wc_customer_order_csv_export_order_row',10,1);
function wc_customer_order_csv_export_order_row($order_data){
	if (!is_array($order_data)) { return $order_data; }
	if (!is_numeric($order_data['cart_discount'])) {
		$order_data['cart_discount'] = 0.00;
	}
	if (!is_numeric($order_data['order_discount'])) {
		$order_data['order_discount'] = 0.00;
	}
	return $order_data;
}