fixed conversion of non-regular c3t3 to TNL mesh

	using MeshType = TetrahedralMesh< typename C3T3::Triangulation::Geom_traits::FT >;

	using PointType = typename MeshType::PointType;

	// NOTE: this function cannot work with the underlying triangulation alone:

	// - c3t3's triangulation contains even points outside the domain (on the

	//   bounding ball).

	// - Moreover, the triangulation may be non-regular after the remeshing

	//   algorithm, i.e. the empty-sphere property may be violated (there may

	//   additional points in the circumsphere of a cell). Especially on highly

	//   non-convex domains, the point may be actually inside the domain, so it

	//   is not counted in c3t3.number_of_far_points() and its in_dimension()

	//   may be > -1.

	// - Consequently, the mesh builder may fail with the error: Some points

	//   were not used for cells.

	// Hence, we need to first find the points that are actually used for cells:

	std::unordered_map<typename C3T3::Triangulation::Vertex_handle, std::size_t> V;

	std::size_t idx = 0;

	for( auto cit = c3t3.cells_in_complex_begin();

		cit != c3t3.cells_in_complex_end();

		cit++ )

	{

		for (int i = 0; i < 4; i++)

			if (V.count(cit->vertex(i)) == 0)

				V[cit->vertex(i)] = idx++;

	}

	// initialize TNL mesh builder

	TNL::Meshes::MeshBuilder< MeshType > builder;

	// NOTE: c3t3's triangulation contains even points outside the domain (on

	// the bounding ball), which is why this function must work with c3t3 even

	// though working with just the triangulation would be easier

	builder.setPointsCount(c3t3.triangulation().number_of_vertices() - c3t3.number_of_far_points());

	builder.setPointsCount(idx);

	builder.setCellsCount(c3t3.number_of_cells());

	// index mapping for vertices in the complex

	std::unordered_map<typename C3T3::Triangulation::Vertex_handle, std::size_t> V;

	// set points

	std::size_t idx = 0;

	for( auto vit : c3t3.triangulation().finite_vertex_handles() )

	{

		if(vit->in_dimension() <= -1) continue;

		V[vit] = idx;

		builder.setPoint(idx++, {vit->point()[0], vit->point()[1], vit->point()[2]});

		if (V.count(vit) == 0)

			continue;

		builder.setPoint(V[vit], {vit->point()[0], vit->point()[1], vit->point()[2]});

	}

	// set cell seeds