message: Fix having null values in value list
diff: @@ -1720,10 +1720,15 @@ Obj ClusterTree::insert(ObjKey k, const FieldValues& values)
  if (Replication* repl = get_alloc().get_replication()) {
  repl->create_object(table, k);
  - for (auto v : values) {
  + for (const auto& v : values) {
  + if (v.value.is_null()) {
  + repl->set_null(table, v.col_key, k, _impl::instr_Set);
  + }
  + else {
  repl->set(table, v.col_key, k, v.value, _impl::instr_Set);
  }
  }
  + }
  return Obj(this, state.mem, k, state.index);
  }
  