message: fix error on unmount (fix
diff: @@ -220,7 +220,11 @@ const createCesiumComponent = <E, P, C, CC = {}, R = {}>(
  opts.unmount(this._ce, this.props.cesium, this.props, this.ref, this._state);
  }
  - if (this._ce) {
  + if (
  + this._ce &&
  + // If element is already destroyed, skip detaching events. (#70)
  + (typeof (this._ce as any).isDestroyed !== "function" || !(this._ce as any).isDestroyed())
  + ) {
  detachEvents(this._ce, CesiumComponent.getCesiumEventMap(this.props));
  }
  