Don't calculate surcharge when no surcharge is set

[DeWitjesNL]

We're using a plug-in called "WooCommerce Deposits" to allow customers to split payments in the webshop. This has worked fine, but some time ago suddenly extra taxes were calculated on the second payment. Of course I've contacted the plug-in author, as it was likely the problem had something to do with the plug-in. Tests however, show that the problem only occurs when using the Mollie gateway. The plug-in author gave me the information below to pass on. Hopefully something can be done to remedy the problem. Thanks!

`After investigating further I have found that the cause of this issue is the surcharge functionality in Mollie payment gateways. Even though the surcharge is not configured, the gateway still adds a fee of $0 which causes the recalculation for the partial payment totals (and taxes) causing this bug.

The solution would be in Mollie payment gateway plug-in authors to limit this functionality only when a surcharge exists, or to limit the functionality to woocommerce normal orders (shop_order post type), or to add a filter to their code allowing 3rd party plug-ins like ours to control when to add surcharge and calculate totals. I would recommend contacting their support regarding these changes. From our side, we will try to make improvements to the partial payments calculations flow so it is less affected by 3rd party plug-ins actions.`

[DaanG47]

+1