message: box argument is optional when setting the section box
diff: @@ -121,7 +121,7 @@ export interface IViewer {
  on(eventType: ViewerEvent, handler: (arg) => void)
  setSectionBox(
  - box: {
  + box?: {
  min: { x: number; y: number; z: number }
  max: { x: number; y: number; z: number }
  },
  