Adjust error massage in SubsamplingVTKWriter
The number of intervals in Dune::RefinementIntervals
that are passed to the SubsamplingVTKWriter should be larger than zero but the error message was talking about negative values not being allowed.
The number of intervals in Dune::RefinementIntervals
that are passed to the SubsamplingVTKWriter should be larger than zero but the error message was talking about negative values not being allowed.