lnitialize payload of additionallnfo for VTS InjectSensorEventData test

If the payload of additionalInfo event isn't initialized, system will
crash when execute to the function of convertToHidlEvent in
HalProxyAidl::injectSensorData. Because there is an operation to get
the payload in the function of convertToHidlEvent.

Bug:306109770
Test:VtsAidlHalSensorsTargetTest.Sensors/SensorsAidlTest #InjectSensorEventData
Change-Id:I649de10451914ddfdb9d735ca1359521bf810bca