Find Contacts / Advanced Search: Record Activity for Contacts bulk action is broken

To recreate:
Use Find Contacts to do a search.
Select 2-3 rows and select 'Record Activity for Contacts' form
When the activity form loads, the 'With Contacts' widget should contain the selected contacts, but it's EMPTY.

NOTE: 'Send Email to Contacts' action uses a similar flow and target widget - and that's working, so check that code for fix approach.