Reset next_consumption_date when copying line

issue7813
review68341002

subscription.py

@@ -701,6 +701,7 @@ class Line(sequence_ordered(), ModelSQL, ModelView):
             default = {}
         else:
             default = default.copy()
+        default.setdefault('next_consumption_date', None)
         default.setdefault('consumed', None)
         return super(Line, cls).copy(lines, default=default)