toMap method Null safety

Implementation

@override
Map<String, Object?> toMap() {
  return Map.from(super.toMap())
    ..addAll({
      'coordinates': this.coordinates.map((coord) => coord.toMap()).toList(),
      'width': this.width,
      'color': this.color?.value.toRadixString(16),
      'lineDashType': this.lineDashType?.index,
    });
}