Add null check in InputManagerService#verifyInputEvent

Using a null event can cause the system to crash.

Bug: 197961435
Fixes: 201720518
Test: Presubmit
Change-Id: Ibf4b44dbedc3b041f6e38362b862f1ab0f665726
(cherry picked from commit 38e3e2b6f6cad87ebbf21a25c42fc2193590fd7e)
1 file changed