fix: Redirect Web Form user directly to success URL, if no amount is due (backport #12661) (#12856)

If there is no amount due when using WebForms which accept payments, redirect the user directly to the success URL. This is useful for free items.

(cherry picked from commit f8f1301b79)

Co-authored-by: ci2014 <christoph.isik@wpci.de>

frappe/website/doctype/web_form/web_form.py

@@ -215,6 +215,11 @@ def get_context(context):
 			amount = self.amount
 			if self.amount_based_on_field:
 				amount = doc.get(self.amount_field)
+
+			from decimal import Decimal
+			if amount is None or Decimal(amount) <= 0:
+				return frappe.utils.get_url(self.success_url or self.route)
+				
 			payment_details = {
 				"amount": amount,
 				"title": title,