add preprocessor protection

amdis/MeshCreator.hpp

@@ -185,9 +185,11 @@ namespace AMDiS
         return read_gmsh_file<HostGrid>(filename, Dune::PriorityTag<42>{});
 #endif
       }
+#if HAVE_DUNE_VTK
       else if (ext == ".vtu") {
         return Dune::VtkReader<HostGrid, Dune::Vtk::LagrangeGridCreator<HostGrid>>::createGridFromFile(filename);
       }
+#endif
       else if (ext == ".1d" || ext == ".2d" || ext == ".3d" || ext == ".amc") {
         return read_alberta_file<HostGrid>(filename, Dune::PriorityTag<42>{});
       }