fstat does not handle badly formatted URLs correctly

[sentry]

Sentry Issue: FSTAT-5

ValueError: unconverted data remains: 'A=0
(3 additional frame(s) were not displayed)
...
  File "app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "controller.py", line 146, in instance_summary
    start_date = parse_start_date(request.args.get('start_date'))
  File "lib.py", line 27, in parse_start_date
    start_date = datetime.strptime(start_date, '%Y-%m-%d')
  File "_strptime.py", line 328, in _strptime
    data_string[found.end():])