vtkVRMLImporter: if non-NULL, delete CurrentTransform in destructor

In normal usage, it will be deleted at ImportEnd time, but in cases
where ImportEnd is never called, it needs to be deleted in the
destructor, too, since it's unconditionally created with New in the
constructor.

Change-Id: I6747d7d8cf641cf3a7fe9fe03fae0716a49fe4a7
Merge topic 'vh1624-dashboard-follow-up' into master

8450ddd1 vtkVRMLImporter: if non-NULL, delete CurrentTransform in destructor