communicator not correct if range is empty

                                }

                            }

                            const auto tempworkers = ::make_communicator(

                            auto tempworkers = ::make_communicator(

                                    workers,

                                    workers.group().exclude(

                                            ranks_to_exclude.begin(),

                                            ranks_to_exclude.end()),

                                    0);

                            // The communicator is not correct if ranks are empty

                            if (workers.size()==1) tempworkers = workers;

                            m_ops.emplace(std::make_pair(

                                    make_pair(input_path, output_path),