Add null check in InputManagerService#verifyInputEvent

Using a null event can cause the system to crash.

Bug: 197961435
Test: Presubmit
Change-Id: Ibf4b44dbedc3b041f6e38362b862f1ab0f665726

services/core/java/com/android/server/input/InputManagerService.java

@@ -900,6 +900,7 @@ public class InputManagerService extends IInputManager.Stub
 
     @Override // Binder call
     public VerifiedInputEvent verifyInputEvent(InputEvent event) {
+        Objects.requireNonNull(event, "event must not be null");
         return nativeVerifyInputEvent(mPtr, event);
     }