toJson method Null safety

Implementation

Map<String, dynamic> toJson() {
  final json = _$OpenChannelParamsToJson(this);
  if (coverImage != null && coverImage!.hasBinary) {
    json['cover_file'] = coverImage;
  } else {
    json['cover_url'] = coverImage?.url;
  }

  json.removeWhere((key, value) => value == null);
  return json;
}