Cannot read property 'status' of undefined error when there is no network

When there is no network the `_request` function fails, without rejecting the Promise, which makes impossible to catch the error when using a callback.

Even though the component can't be used without the network (#388), I think would be good to handle the case.

The error:

`TypeError: Cannot read property 'status' of undefined`

首先定位 `_request` 函式，並重現 issue 中描述的無網路情況。檢查 issue #388 中的相關脈絡，接著確保失敗的請求 reject 其 Promise，讓 callback 使用者能夠捕捉錯誤；當未定義的 `status` 錯誤得到處理而不是逸出時，即表示完成。

由索引模型根據 Issue 內容生成。