0.6.6-dev - UnhandledPromiseRejectionWarning after 2 minutes if vacuum battery is empty/off
```
[2020-2-1 13:35:53] [Staubsauger OG Bad] DEB getDevice | Discovering vacuum cleaner
[2020-2-1 13:35:55] [Staubsauger OG Bad] ERR connect | miio.device, next try in 2 minutes | Error: Could not connect to device, handshake timeout
 (node:17374) UnhandledPromiseRejectionWarning: Error: Could not connect to device, handshake timeout
     at Timeout._onTimeout (/usr/lib/node_modules/homebridge-xiaomi-roborock-vacuum/node_modules/miio/lib/network.js:432:17)
     at listOnTimeout (internal/timers.js:531:17)
     at processTimers (internal/timers.js:475:7)
 (node:17374) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 3)
```

Sorry @afharo 