Update the vtkVolume in the vtkVolumeInputHelper when updating inputs
The Volume member of vtkVolumeInputHelper could hold onto a reference to a deleted vtkVolume. Ensure it is updated to the current vtkVolume in vtkOpenGLGPUVolumeRayCastMapper::vtkInternal::UpdateInputs().
Backport: paraview/release
Edited by Cory Quammen