tracing without participant #3860

added check for nil on participant before saving.
this might happen if the participant is in eligible and deleted.

closes #3860
Added checks around contacts #3860

Contact relationships to participants in tracing module
should not be saved if the participant is nil
Merge pull request #130 from NUBIC/3860_ineligible_participant_tracing_module

tracing without participant #3860

adding to 1.5.1 hotfix