fix: validate items against selling settings (#45288)

fix: validate_for_duplicate_items

Co-authored-by: Sanket322 <shahsanket322003.com>

erpnext/controllers/accounts_controller.py

@@ -3719,6 +3719,7 @@ def update_child_qty_rate(parent_doctype, trans_items, parent_doctype_name, chil
 						).format(frappe.bold(parent.name))
 					)
 	else:  # Sales Order
+		parent.validate_for_duplicate_items()
 		parent.validate_warehouse()
 		parent.update_reserved_qty()
 		parent.update_project()