VTK-3604 - fallback to 1 thread if Blob and Worker are not supported
VTK-3604 - fallback to 1 thread if Blob and Worker are not supported

vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk