Update sales_order.py
diff --git a/erpnext/selling/doctype/sales_order/sales_order.py b/erpnext/selling/doctype/sales_order/sales_order.py
index 158c726..7e008da 100644
--- a/erpnext/selling/doctype/sales_order/sales_order.py
+++ b/erpnext/selling/doctype/sales_order/sales_order.py
@@ -337,8 +337,6 @@
 	def postprocess(source, doc):
 		doc.material_request_type = "Purchase"
 
-	so = frappe.get_doc("Sales Order", source_name)
-
 	doc = get_mapped_doc("Sales Order", source_name, {
 		"Sales Order": {
 			"doctype": "Material Request",
@@ -352,7 +350,7 @@
 				"parent": "sales_order",
 				"stock_uom": "uom"
 			}
-		}.
+		},
 		"Sales Order Item": {
 			"doctype": "Material Request Item",
 			"field_map": {