Accessing nonexistent reg causes 500 error, not 404

[lbeaufort]

From the logs

https://dev.fec.gov/regulations/400-22/CURRENT
Server error

   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT ERROR:django.request:Internal Server Error: /regulations/400-22/CURRENT
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT Traceback (most recent call last):
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT   File "/home/vcap/deps/0/python/lib/python3.7/site-packages/django/core/handlers/exception.py", line 41, in inner
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT     response = get_response(request)
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT   File "/home/vcap/deps/0/python/lib/python3.7/site-packages/django/core/handlers/base.py", line 249, in _legacy_get_response
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT     response = self._get_response(request)
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT   File "/home/vcap/deps/0/python/lib/python3.7/site-packages/django/core/handlers/base.py", line 187, in _get_response
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT     response = self.process_exception_by_middleware(e, request)
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT   File "/home/vcap/deps/0/python/lib/python3.7/site-packages/django/core/handlers/base.py", line 185, in _get_response
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT     response = wrapped_callback(request, *callback_args, **callback_kwargs)
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT   File "/home/vcap/deps/0/src/regulations/regulations/views/redirect.py", line 49, in redirect_by_current_date
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT     return redirect_by_date_str(request, label_id, date.today().isoformat())
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT   File "/home/vcap/deps/0/src/regulations/regulations/views/redirect.py", line 17, in redirect_by_date_str
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT     for struct in client.regversions(label_id.split('-')[0])['versions']:
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT TypeError: 'NoneType' object is not subscriptable
   2020-08-25T11:53:02.68-0400 [APP/PROC/WEB/0] OUT 10.255.169.50 - - [25/Aug/2020:11:53:02 -0400] "GET /regulations/400-22/CURRENT HTTP/1.1" 500 27 "-" "Amazon CloudFront"

https://dev.fec.gov/regulations/200-22/CURRENT gets 404