fix: skip warning for free items

(cherry picked from commit 772776a)

erpnext/controllers/accounts_controller.py

@@ -1903,22 +1903,22 @@ def validate_multiple_billing(self, ref_dt, item_ref_dn, based_on):
 				continue
 
 			ref_amt = flt(reference_details.get(item.get(item_ref_dn)), self.precision(based_on, item))
+			based_on_amt = flt(item.get(based_on))
 
 			if not ref_amt:
-				frappe.msgprint(
-					_("System will not check over billing since amount for Item {0} in {1} is zero").format(
-						item.item_code, ref_dt
-					),
-					title=_("Warning"),
-					indicator="orange",
-				)
+				if based_on_amt:  # Skip warning for free items
+					frappe.msgprint(
+						_(
+							"System will not check over billing since amount for Item {0} in {1} is zero"
+						).format(item.item_code, ref_dt),
+						title=_("Warning"),
+						indicator="orange",
+					)
 				continue
 
 			already_billed = self.get_billed_amount_for_item(item, item_ref_dn, based_on)
 
-			total_billed_amt = flt(
-				flt(already_billed) + flt(item.get(based_on)), self.precision(based_on, item)
-			)
+			total_billed_amt = flt(flt(already_billed) + based_on_amt, self.precision(based_on, item))
 
 			allowance, item_allowance, global_qty_allowance, global_amount_allowance = get_allowance_for(
 				item.item_code, item_allowance, global_qty_allowance, global_amount_allowance, "amount"