diff -r d5a4094774e9 sale.py
--- a/trytond/trytond/modules/sale_supply_drop_shipment/sale.py	Wed Oct 04 22:04:03 2017 +0200
+++ b/trytond/trytond/modules/sale_supply_drop_shipment/sale.py	Fri Oct 06 14:55:49 2017 +0200
@@ -58,7 +58,8 @@
         moves = []
         for line in self.lines:
             moves += line.get_drop_moves()
-        Move.save(moves)
+        if moves:
+            Move.save(moves)
 
 
 class SaleLine: