Fix possible NPE in DPMS.

If there's no ActiveAdmin for the given user then the ternary
expression would return null, which immediately will throw an NPE as it
gets auto-unboxed into from Boolean to boolean.

Bug: 217923092
Test: errorprone build
Change-Id: I4043f0061e5a23e4d5aa408917f6d51b8bbf22ec