Comparison of date with nil #4384

In the cases where the event start date is nil
simply push those events to the bottom of the
list of events
Update to float #4384

based on comment
Merge branch 'develop' into 4384-date_nil_comparison

Conflicts:
	app/models/participant_consent.rb
Merge branch 'develop' of ssh://github.com/NUBIC/ncs_navigator_core into develop