刪除最後一頁的最後一條數據，沒回到前一頁

// 更新當前頁碼
            let totalPage = Math.ceil((this.totalNum - 1)/this.pageSize);
            let currentPage = this.currentPage > totalPage ? totalPage : this.currentPage;
            this.currentPage = this.currentPage < 1 ? 1 : currentPage;

參考博客：http://www.javashuo.com/article/p-aypwjyfo-nn.html