[vtkusers] Widgets and RemoveAllProps

[Luca Picello]

Having a renderwindow with a splinewidget and calling RemoveAllProps() 
what happen exactly?
I can see the actors are removed from the renderwindow and even of 
forcing them to appear they are not rendered anymore. (calling On() for 
splinewidget for example)
however the referencecounter of the object is not modified...
can somebody deeply explain to me what is expected to happen?
thank you

luca