Data I/O event implicit variable returns null for some node types

Case when the implicit event variable is null:
Signal event
Error event
Escalation event

For timer node the returned value is a number. Is that correct? For example java.lang.Long

Steps to reproduce:
1. Import attached assets into Business central
2. Build & deploy the project
3. Consult Logs of application servers to see the value of `event` variable

For tests on all node types see - https://github.com/bpmn-tutorials/ThrowCatchEventsTest