java.lang.NullPointerException when random_selector default feature isn't found

Datapacks upgraded from 1.16 say "Failed to load datapacks, can't proceed with server load, java.lang.NullPointerException: Cannot invoke "crn.d()" because the return value of "java.util.function.Supplier.get()" is null" - Not sure what the reason is. Datapack was working fine in snapshots before 1.17 release.