[vtkusers] Error Raised in Tcl.

[D.M.P.Davies]

Gurus,

I use (a few) vtkThreshold instances using cell values  on an
unstructured grid. On each of the extracted grids I plot the scalar
contours using vtkContour Filter instances.

Problem : When starting some of the extracted grids are null which
results (once) with the tcl error raised of no data ...

Is there a way to stop this error being raised in Tcl??

Many Thanks

Dave Davies