蓝牙与设备建立连接后，发送几次数据即报出如下异常：
Bug:
at Windows.Storage.Streams.DataWriter.StoreAsync()
at sdkBluetoothA2DWP8CS.MainPage.<sendData>d__12.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__0(Object state)
Message:The object has been closed. (Exception from HRESULT: 0x80000013)
