Array comparison fails #3521

when one of the comparative array elements is nil.

This fix for #3521 should move the scoping items into the model
p_type is not being set for birth cohort #3511

This fix should correct the immediate problem of not setting the
participant type for the birth cohort participants, but the larger issue
of not creating the ppg_details and other operational data on the
participant who is recruited via this instrument will need to be addressed
here.
1.4.0.rc5