[vtkusers] vtkGPUVolumeRayCastMapper crash with Apple machines fixed.

[Francois Bertel]

Hello,

I think I fixed the crash that some Mac users reported when they use
the vtkGPUVolumeRayCastMapper.
The fix in rev 1.4 of VTK/VolumeRendering/vtkOpenGLGPUVolumeRayCastMapper.cxx

It still not supported on Mac but it nows return gracefully instead of crashing.


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François Bertel, PhD  | Kitware Inc. Suite 204
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