fixes for conversion factor in old invoices

controllers/buying_controller.py

@@ -331,6 +331,9 @@ class BuyingController(AccountsController):
 	# update valuation rate
 	def update_valuation_rate(self, parentfield):
 		for d in self.doclist.get({"parentfield": parentfield}):
+			d.conversion_factor = d.conversion_factor or webnotes.conn.get_value(
+				"UOM Conversion Detail", {"parent": d.item_code, "uom": d.uom}, 
+				"conversion_factor") or 1
 			if d.item_code and d.qty:
 				# if no item code, which is sometimes the case in purchase invoice, 
 				# then it is not possible to track valuation against it