[vtkusers] vtkAppendPolyData bug

[David Doria]

At line 239 in vtkAppendPolyData.cxx, there is:

  if ( numPts < 1 || numCells < 1 )
    {
    vtkDebugMacro(<<"No data to append!");
    return 1;
    }

this prevents the polydata's from being appended if there are no
cells, even if there are points. I think it should be changed to
  if ( numPts < 1 && numCells < 1 )

so that only if there are no points and no cells it should fail.

Anyone agree/disagree?

Thanks,

David