[Regression] Var type properties are not initialized before access is possible

If a component defines a var property with an Array or Object initializer, that property can be accessed before initialization. This causes an error stating that the property is undefined.

It is difficult to protect against this behavior in more complex use cases since the Component.onCompleted signal ordering is not defined.

We have primarily observed this behavior with var properties as indicated in the attached example, however we cannot say definitively whether this may happen with basic QML types as well.