stopShowingGlow(duration) {
    if (this._isGlowing) {
      this._isGlowing = false;

      return this.whenRequiredResourcesReady().then((requestId) => {
        if (!this.getAreResourcesValid(requestId)) return; // load invalidated or resources changed

        if (this._glowImageMap != null) {
          if (duration == null) { duration = 0.0; }
          this._glowImageMap.fadeToInvisible(duration);
        }
      });
    }
  }
Stops showing the loot crate as glowing.
@param {Number} [duration=0.0]
@public
@return {Promise}