Failed to connect to Mi Kettle-TypeError: Cannot read property 'StartNotify' of undefined

Hi everyone,

I follow the readme to install the package.
I've cloned the repo, done npm install, configured cybele as follows

```
{
"mqtt": {
"url": "MQTT"
},
"dongles": [
{
"hciDevice": "hci0",
"mode": "le",
"services": [],
"devices": [{
"type": "MiKettleDevice",
"friendlyName": "Mi Kettle",
"mac": "MAC",
"productId":1116
}

]
}
]
}
```
```
Connected to MQTT Broker
Startup complete
/home/pi/Cybele/lib/devices/MiKettle/MiKettleDevice.js:166
this.characteristicsByUUID[MiKettleDevice.CHARACTERISTICS.auth].StartNotify([], err => {
^

TypeError: Cannot read property 'StartNotify' of undefined
at /home/pi/Cybele/lib/devices/MiKettle/MiKettleDevice.js:166:73
at Object.item.task (/home/pi/Cybele/node_modules/semaphore/lib/semaphore.js:40:29)
at Object.take (/home/pi/Cybele/node_modules/semaphore/lib/semaphore.js:51:9)
at MiKettleDevice.doAuthStageTwo (/home/pi/Cybele/lib/devices/MiKettle/MiKettleDevice.js:165:20)
at Object. (/home/pi/Cybele/lib/devices/MiKettle/MiKettleDevice.js:156:22)
at EventEmitter. (/home/pi/Cybele/node_modules/dbus-native/lib/bus.js:138:19)
at EventEmitter.emit (events.js:388:22)
at /home/pi/Cybele/node_modules/dbus-native/index.js:106:14
at Socket. (/home/pi/Cybele/node_modules/dbus-native/lib/message.js:55:9)
at Socket.emit (events.js:376:20)

```

Any ideas what's wrong?