code: function safeGetWaypoints(connection) {
  
    var waypoints = connection.waypoints;
  
    if (!waypoints.length) {
      throw new Error('connection#' + connection.id + ': no waypoints');
    }
  
    return waypoints;
  }
docs: Return waypoints of given connection; throw if non exists (should not happen!!).
  
  @param {Connection} connection
  
  @return {Array<Point>}