The way it works is that an instance of your custom class is created automaticaly. This is also exactly what happens if you declare a public (or [Serializable] private) variable in a MonoBehaviour (so that it can be inspected).
So, at least at this point, a custom class variable can not be null. The best way to work with it, would be with dynamic variables.
I will see for the next version to start a custom class variable as null and create an instance optionaly thought.
As for your 3rd question, it seems that you are declaring this on a typical MonoBehaviour class instead of an ActionTask or ConditionTask. Am I correct?
Gavalakis
