fix for the update button in the sales invoice (#13435)

diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 1af2fdd..d690241 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -666,7 +666,9 @@
 			self.remove(item)
 
 	def set_payment_schedule(self):
-		if self.doctype == 'Sales Invoice' and self.is_pos: return
+		if self.doctype == 'Sales Invoice' and self.is_pos:
+			self.payment_terms_template = ''
+			return
 
 		posting_date = self.get("bill_date") or self.get("posting_date") or self.get("transaction_date")
 		date = self.get("due_date")
diff --git a/erpnext/public/js/controllers/transaction.js b/erpnext/public/js/controllers/transaction.js
index eae5283..9ed20c9 100644
--- a/erpnext/public/js/controllers/transaction.js
+++ b/erpnext/public/js/controllers/transaction.js
@@ -106,7 +106,8 @@
 		}
 
 		if(
-			this.frm.fields_dict["payment_terms_template"]
+			this.frm.docstatus < 2 
+			&& this.frm.fields_dict["payment_terms_template"]
 			&& this.frm.fields_dict["payment_schedule"]
 			&& this.frm.doc.payment_terms_template
 			&& !this.frm.doc.payment_schedule.length