Use correct disposition category in view #3605

The correct category for email/website contact is
General Study Visit.

Closes #3605
Merge branch 'master' of https://github.com/NUBIC/ncs_navigator_core
Merge branch 'master' of https://github.com/NUBIC/ncs_navigator_core
Check for nil

Return 0 for repeat_key if participant is nil
Check participant existence before calling advance
Put call to build activity_plan after check #3602

If the participant is nil then there is no plan to build
Ineligible participant has no PSC association #3609

The psc activities_for_event method expects a participant
association for the event. But recent changes delete the participant
if found ineligible. This change checks that association exists and if
not returns an empty array.