encode method Null safety

Implementation

Object encode() {
  final Map<Object?, Object?> pigeonMap = <Object?, Object?>{};
  pigeonMap['id'] = id;
  pigeonMap['trackType'] = trackType?.index;
  pigeonMap['name'] = name;
  pigeonMap['trackSubtype'] = trackSubtype?.index;
  pigeonMap['contentId'] = contentId;
  pigeonMap['language'] = language;
  return pigeonMap;
}