toJson method Null safety

Implementation

Map<String, dynamic> toJson() {
  final Map<String, dynamic> data = <String, dynamic>{};
  data['durationInformation'] = durationInformation.toJson();
  data['difficultyInformation'] = difficultyInformation.toJson();
  data['minutesPlayed'] = minutesPlayed;
  data['questionsAnswered'] = questionsAnswered;
  data['elo'] = elo;
  data['questionsRightAnswered'] = questionsRightAnswered;
  data['categoryInformation'] = categoryInformation.toJson();
  data['username'] = username;
  return data;
}