Fix an NPE that occurs during dock setup on tangor.

This also prevents continuing setup past the intro screen.

Bug: 412208020
Test: Manually by enabling and disabling the dreams_v2 flag and invoking
the dream setting screen both in Settings and in setup.
Flag: android.service.dreams.dreams_v2

Change-Id: I3a2f006dd65bb026192c6d0a6e9eb19c7ef6c40f