fromMap method Null safety

Implementation

@override
fromMap(Map map) {
  // ignore: unnecessary_null_comparison
  if (map == null) {
    return null;
  }
  return BMFRouteLine(
      distance: map['distance'],
      duration: BMFTime.fromMap(map['duration']),
      starting: BMFRouteNode.fromMap(map['starting']),
      terminal: BMFRouteNode.fromMap(map['terminal']),
      title: map['title']);
}