Fix export feb
Replaced vtkUnstructuredGrid with vtkPointSet in mesh operations, so that the conversion always succeeds. Add support for empty volume meshes.
Together with !36 (merged), aeva#172 (closed) should be addressed.
Replaced vtkUnstructuredGrid with vtkPointSet in mesh operations, so that the conversion always succeeds. Add support for empty volume meshes.
Together with !36 (merged), aeva#172 (closed) should be addressed.