При активации единственной имеющейся сетки вещания возникает ошибка 500

[einsfr]

Internal Server Error: /schedule/lineups/activate/json/ Traceback (most recent call last):
File "/home/alex/mmkit/venv/lib/python3.4/site-packages/django/core/handlers/base.py", line 132, in get_response
response = wrapped_callback(request, _callback_args, *_callback_kwargs)
File "/home/alex/mmkit/venv/lib/python3.4/site-packages/django/contrib/auth/decorators.py", line 22, in _wrapped_view
return view_func(request, _args, *_kwargs)
File "/home/alex/mmkit/venv/lib/python3.4/site-packages/django/views/decorators/http.py", line 45, in inner
return func(request, _args, *_kwargs)
File "./efsw/schedule/views.py", line 370, in lineup_activate_json
current_active_lineup.active_until = activation_date - datetime.timedelta(days=1)
AttributeError: 'NoneType' object has no attribute 'active_until'