message: Minor improvement of Cluster::dump_objects
diff: @@ -1465,6 +1465,10 @@ void Cluster::dump_objects(int64_t key_offset, std::string lead) const
  }
  std::cout << lead << "key: " << std::hex << key_value + key_offset << std::dec;
  for (size_t j = 1; j < size(); j++) {
  + if (m_tree_top.get_spec().get_column_attr(j - 1).test(col_attr_List)) {
  + std::cout << ", list";
  + }
  +
  switch (m_tree_top.get_spec().get_column_type(j - 1)) {
  case col_type_Int: {
  bool nullable = m_tree_top.get_spec().get_column_attr(j - 1).test(col_attr_Nullable);
  @@ -1535,7 +1539,12 @@ void Cluster::dump_objects(int64_t key_offset, std::string lead) const
  ArrayTimestamp arr(m_alloc);
  ref_type ref = Array::get_as_ref(j);
  arr.init_from_ref(ref);
  + if (arr.is_null(i)) {
  + std::cout << ", " << "null";
  + }
  + else {
  std::cout << ", " << arr.get(i);
  + }
  break;
  }
  case col_type_Link: {
  