[vtkusers] Correct use of Delete()

[Siarhei Ryshkevich]

Hi,

I created a plane source, a mapper and an actor. In the next lines I deleted the mapper and plane source objects using Delete(), but left the actor. Surprisingly, everything works fine.
I'm assuming that mapper is not actually because of use of the reference count. Is it deleted later?
Is it a bad practise?  Will I ran into some trouble with memory?

Best Regards