toJson method Null safety

Implementation

@override
Map<String, dynamic> toJson() {
  final json = <String, dynamic>{};
  json['type'] = type;
  json.addAll({
    'message': message?.toJson(),
    'time': time,
    'level': level,
    'sequenceNumber': sequenceNumber,
    'loggerName': loggerName?.toJson(),
    'zone': zone?.toJson(),
    'error': error?.toJson(),
    'stackTrace': stackTrace?.toJson(),
  });
  return json;
}