TypeError: '>=' not supported between instances of 'NoneType' and 'tuple'

[sentry]

Sentry Issue: BUILDHUB2-5

TypeError: '>=' not supported between instances of 'NoneType' and 'tuple'
(1 additional frame(s) were not displayed)
...
  File "whitenoise/middleware.py", line 57, in __call__
    response = self.process_request(request)
  File "whitenoise/middleware.py", line 68, in process_request
    return self.serve(static_file, request)
  File "whitenoise/middleware.py", line 72, in serve
    response = static_file.get_response(request.method, request.META)
  File "whitenoise/responders.py", line 45, in get_response
    if self.is_not_modified(request_headers):
  File "whitenoise/responders.py", line 185, in is_not_modified
    return parsedate(last_requested) >= self.last_modified

TypeError: '>=' not supported between instances of 'NoneType' and 'tuple'

[jcristau]

This was fixed by evansd/whitenoise#287 in 5.3.0, but we're using 5.2.0.