message: Fix an assertion error in ClassMerging
  Summary: When the number of the remaining classes is less than the min-count, we clean the current group.
diff: @@ -402,14 +402,15 @@ void Model::create_mergers_helper(
  for (auto it = group_values.begin(); it != group_values.end(); ++it) {
  auto mergeable = *it;
  curr_group.insert(mergeable);
  - if (((curr_group.size() == *max_mergeables_count &&
  + if ((curr_group.size() == *max_mergeables_count &&
  remaining_mergeable_cnt - *max_mergeables_count > 1) ||
  - std::next(it) == group_values.end()) &&
  - curr_group.size() >= min_mergeables_count) {
  + std::next(it) == group_values.end()) {
  + if (curr_group.size() >= min_mergeables_count) {
  create_merger_helper(
  merger_type, shape, group_key, curr_group, interdex_subgroup_idx,
  boost::optional<InterdexSubgroupIdx>(subgroup_cnt++));
  remaining_mergeable_cnt -= curr_group.size();
  + }
  curr_group.clear();
  }
  }
  