[FIX] account_payment_pro: Problema al querer generar una nota de deb…

…ito desde un pago con impuesto NA

Ticket: 76253

account_payment_pro/wizards/account_payment_invoice_wizard.py

@@ -143,7 +143,7 @@ def _compute_amount_untaxed(self):
         self.ensure_one()
         tax_percent = 0.0
         for tax in self.tax_ids.filtered(
-                lambda x: not x.price_include):
+                lambda x: not x.price_include and x.amount_type not in ['fixed']):
             if tax.amount_type == 'percent':
                 tax_percent += tax.amount
             elif tax.amount_type == 'partner_tax':