post challenge submissions throw an error

[spMohanty]

```2018-11-22T13:31:54.606504+00:00 app[web.4]: 23 TID-gsdaazoh3 INFO: [Rollbar] Success

2018-11-22T13:31:54.606629+00:00 app[web.4]: 23 TID-gsdaazoh3 INFO: [Rollbar] Details: https://rollbar.com/instance/uuid?uuid=ed05a2c2-14dd-4836-a74b-7a65bad56f50 (only available if report was successful)

2018-11-22T13:31:54.608060+00:00 app[web.4]: 23 TID-gsdaazoh3 FATAL:   

2018-11-22T13:31:54.608280+00:00 app[web.4]:   [1m[35m (2.0ms)[0m  [1m[35mBEGIN[0m

2018-11-22T13:31:54.609118+00:00 app[web.4]: 23 TID-gsdaazoh3 FATAL: ArgumentError (comparison of ActiveSupport::TimeWithZone with nil failed):

2018-11-22T13:31:54.609143+00:00 app[web.4]: 23 TID-gsdaazoh3 FATAL:   

2018-11-22T13:31:54.609197+00:00 app[web.4]: 23 TID-gsdaazoh3 FATAL: app/models/submission.rb:49:in `>'```

Seems to be hapenning here : https://github.com/crowdAI/crowdai/blob/master/app/models/submission.rb#L49

[scarroll32]

Do we know which challenge this is for ?

[scarroll32]

There are overlapping rounds on the challenge -- this was not planned for.

Round 2 (current)

Round 3 (future)

[scarroll32]

Challenge

Round 3 deleted. Please try again @spMohanty