BUG:Fixed double *GetBounds() on vtkAbstractMapper3D subclasses. In vtkAbstractMapper3D, GetCenter() and GetLength() call GetBounds and rely on the side effect that it will update this->Bounds, the subclasses implementations were not changing this->Bounds to uninitialized (1,-1,1,-1,1,-1) and were returning some arbitrary (-1,1,-1,1,-1,1) valid bounds instead when the input is null. It could be problematic if the scene has one mapper with a valid input with bounds out of (-1,1,-1,1-1,1) and another mapper with an empty input. Fixed another bug in vtkCompositePolyDataMapper2.cxx where input can be used before checking it is not null.