toMap method Null safety

Implementation

Map<String, dynamic> toMap() {
  HashMap<String, dynamic> dic = HashMap.of({
    'url': url,
    'roomId': roomId,
    'uid': uid,
    'mixType': mixType.value,
    'video': video.toMap(),
    'layout': layout.toMap(),
    'audio': audio.toMap(),
  });
  if (authInfo != null) {
    dic['authInfo'] = authInfo;
  }
  return dic;
}