message: fix indexing issu
diff: @@ -532,9 +532,11 @@ namespace RINGMesh
  const std::vector< index_t >& polygon_ptr )
  {
  for( auto p : range( polygon_ptr.size() - 1 ) ){
  - std::vector< index_t > polygon_vertices(
  - &polygons[ polygon_ptr[p] ],
  - &polygons[ polygon_ptr[p + 1] - 1 ]);
  + index_t first = polygon_ptr[p];
  + index_t last = polygon_ptr[p + 1];
  + const std::vector< index_t > polygon_vertices(
  + &polygons[first],
  + &polygons[last]);
  do_create_polygon( polygon_vertices );
  }
  clear_polygon_linked_objects();
  