Fixed unitialized memory access bug.
Fixed unitialized memory access bug.

Extent was being accessed before being initialized.

sumedhasingla/VTK,keithroe/vtkoptix,sumedhasingla/VTK,sumedhasingla/VTK,keithroe/vtkoptix,sumedhasingla/VTK,sumedhasingla/VTK,SimVascular/VTK,keithroe/vtkoptix,sumedhasingla/VTK,SimVascular/VTK,SimVascular/VTK,keithroe/vtkoptix,SimVascular/VTK,SimVascular/VTK,keithroe/vtkoptix,keithroe/vtkoptix,SimVascular/VTK,sumedhasingla/VTK,keithroe/vtkoptix,SimVascular/VTK,sumedhasingla/VTK,SimVascular/VTK,keithroe/vtkoptix