wrong release function in async example #4

  release(item) {
    const index = this.items.indexOf(item);
    if (index < 0) throw new Error('Pool: release unexpected item');
    if (this.free[index]) throw new Error('Pool: release not captured');
    this.free[index] = true;
    this.available++;
    if (this.queue.length > 0) {
      const { resolve, timer } = this.queue.shift();
      clearTimeout(timer);
      if (resolve) setTimeout(resolve, 0, item);
    }
  }

  release(item) {
    const index = this.items.indexOf(item);
    if (index < 0) throw new Error('Pool: release unexpected item');
    if (this.free[index]) throw new Error('Pool: release not captured');
    if (this.queue.length > 0) {
      const { resolve, timer } = this.queue.shift();
      clearTimeout(timer);
      if (resolve) setTimeout(resolve, 0, item);
    } else { 
      this.free[index] = true;
      this.available++;
    }
  }