Initialize array pointer to nullptr am: b7a8ee1632 am: d135e1cee9 am: e2bc24f74c

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/keymaster/+/15325714

Change-Id: Id5ef5598917f40c23d1c3bdfbcddf9a62c65d36f