Crash on non-eng builds due to lacking null check.

On eng builds we have an event consistency verifier to log any
inconsistent event stream states due to mishandling of intercepted
events by an accessibility service. On non-eng builds this verifier
is null and a null check was lacking.

bug:8616711

Change-Id: Ib083a405dfa8340025090a65e50155eb10526a90