Ensure that the computed traces of a stock move have a lot

For example the production module may include input or output moves without
lot.

Closes #14396
(grafted from aa1bb0828ed19d9612d40b4fa2a242178edc54ec)

--HG--
branch : 7.0

modules/stock_lot/stock.py

@@ -256,7 +256,7 @@ class LotTrace(ModelSQL, ModelView):
 
     @classmethod
     def _is_trace_move(cls, move):
-        return move.state == 'done'
+        return move.state == 'done' and move.lot
 
     @classmethod
     def _trace_move_order_key(cls, move):