fix: Cannot read properties of undefined (reading 'price_list_rate') …

…(backport #43376) (#43377)

fix: Cannot read properties of undefined (reading 'price_list_rate') (#43376)

(cherry picked from commit a63dca0)

Co-authored-by: rohitwaghchaure <rohitw1991@gmail.com>

erpnext/public/js/controllers/transaction.js

@@ -1102,7 +1102,7 @@ erpnext.TransactionController = class TransactionController extends erpnext.taxe
 
 	apply_discount_on_item(doc, cdt, cdn, field) {
 		var item = frappe.get_doc(cdt, cdn);
-		if(!item.price_list_rate) {
+		if(!item?.price_list_rate) {
 			item[field] = 0.0;
 		} else {
 			this.price_list_rate(doc, cdt, cdn);