Strange logic for supplier invoice

If you create a supplier invoice using the web client (e.g. with Odoo), you first select the partner and then want to add an invoice item. However, the default icon when you want to add an invoice line is the "Save parent record" icon. So you will get the error message "Invalid form, correct red fields" because the field "Total" is undefined yet (you have not selected any invoice entry yet).
The only way to proceed is to put an amount in "Total" and then you can proceed.

It would be more logical to have the icon "Create new record" by default on the "Invoice Lines" section on the right.