toMap method Null safety

Implementation

@override
Map<String, Object?> toMap() {
  return {
    'id': this.id,
    'maxZoom': this.maxZoom,
    'minZoom': this.minZoom,
    'visibleMapBounds': this.visibleMapBounds.toMap(),
    'maxTileTmp': this.maxTileTmp,
    'tileLoadType': this.tileLoadType.index,
    'url': this.url
  };
}