Add null checks

Lint is being updated, and a type that used to be non-null
is now nullable, and needs to be null checked.

Bug: 247885568
Test: Presubmits
Change-Id: I7fc09a9d2d312485071364279c448550e3a1e124
Merged-In: Ie6eaf061d74bd773742aa47f731e95e4b137f438
1 file changed