message: fix missing underscore
diff: @@ -84,7 +84,7 @@ export class StructureLookup3D implements Lookup3D<Element> {
  _boundary: { box: Box3D; sphere: Sphere3D; } | undefined = void 0;
  get boundary() {
  - if (this.boundary) return this._boundary!;
  + if (this._boundary) return this._boundary!;
  this._boundary = computeStructureBoundary(this.structure);
  return this._boundary!;
  }
  