V3.1.2 - TH16 with ds18b20 sensor
**What issue do you have? Please be as thorough and explicit as possible.**

I have 5 TH16 at my home, 4 of them have AM2301 sensors that can read temperature and humidity, and only has a ds18b20 sensor, that measures temperature only, it has no humidity readings.

All TH16 with AM2301 are fine with V3.1.2, but the one with ds18b20 (TH16 Cozinha) is not working properly, the temp reading is fine, but the switch is not functioning.

At V3.0.0, TH16 with ds18b20 only issue is that it shows an alarm at apple homekit icon, I believe due to humidity reading failure, but switch works fine.

**Details of your setup.**
Do you use Homebridge or HOOBS?

Homebridge

Which version of Homebridge/HOOBS do you have?

Homebridge v1.2.3
Node.js v12.18.4
Npm v6.14.8

Which version of this plugin (homebridge-ewelink) do you have?

homebridge-ewelink v3.1.2

**Please paste any relevant logs below. It helps if you can turn `debug` and `debugReqRes` in the package settings for more thorough logging.**
> If you are posting an error then it is helpful for me to also see the previous few lines as this can show the cause of the error.

0|homebridge  | [9/27/2020, 3:15:25 PM] [eWeLink] [TH16 Cozinha] could not be updated as TypeError: Cannot read property 'Switch' of undefined
0|homebridge  |     at deviceThermostat.internalThermostatUpdate (/usr/local/lib/node_modules/homebridge-ewelink/lib/device/thermostat.js:15:58)
0|homebridge  |     at Characteristic.<anonymous> (/usr/local/lib/node_modules/homebridge-ewelink/lib/eWeLink.js:612:65)
0|homebridge  |     at Characteristic.emit (events.js:315:20)
0|homebridge  |     at Characteristic.EventEmitter.emit (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/EventEmitter.js:60:38)
0|homebridge  |     at Characteristic._this.setValue (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Characteristic.js:369:23)
0|homebridge  |     at /usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Accessory.js:967:36
0|homebridge  |     at Array.forEach (<anonymous>:null:null)
0|homebridge  |     at Bridge.Accessory._this._handleSetCharacteristics (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Accessory.js:835:18)
0|homebridge  |     at HAPServer.emit (events.js:315:20)
0|homebridge  |     at HAPServer.EventEmitter.emit (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/EventEmitter.js:60:38)
0|homebridge  |     at HAPServer._this._handleCharacteristics (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/HAPServer.js:731:23)
0|homebridge  |     at IncomingMessage.<anonymous> (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/HAPServer.js:240:39)
0|homebridge  |     at IncomingMessage.emit (events.js:315:20)
0|homebridge  |     at endReadableNT (_stream_readable.js:1220:12)
0|homebridge  |     at processTicksAndRejections (internal/process/task_queues.js:84:21)
0|homebridge  | .
0|homebridge  | [9/27/2020, 3:15:25 PM] [eWeLink] [TH16 Cozinha] requesting previous state to revert Homebridge state.
0|homebridge  | [9/27/2020, 3:15:29 PM] [eWeLink] [TH16 Cozinha] could not be updated as TypeError: Cannot read property 'Switch' of undefined
0|homebridge  |     at deviceThermostat.internalThermostatUpdate (/usr/local/lib/node_modules/homebridge-ewelink/lib/device/thermostat.js:15:58)
0|homebridge  |     at Characteristic.<anonymous> (/usr/local/lib/node_modules/homebridge-ewelink/lib/eWeLink.js:612:65)
0|homebridge  |     at Characteristic.emit (events.js:315:20)
0|homebridge  |     at Characteristic.EventEmitter.emit (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/EventEmitter.js:60:38)
0|homebridge  |     at Characteristic._this.setValue (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Characteristic.js:369:23)
0|homebridge  |     at /usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Accessory.js:967:36
0|homebridge  |     at Array.forEach (<anonymous>:null:null)
0|homebridge  |     at Bridge.Accessory._this._handleSetCharacteristics (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Accessory.js:835:18)
0|homebridge  |     at HAPServer.emit (events.js:315:20)
0|homebridge  |     at HAPServer.EventEmitter.emit (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/EventEmitter.js:60:38)
0|homebridge  |     at HAPServer._this._handleCharacteristics (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/HAPServer.js:731:23)
0|homebridge  |     at IncomingMessage.<anonymous> (/usr/local/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/HAPServer.js:240:39)
0|homebridge  |     at IncomingMessage.emit (events.js:315:20)
0|homebridge  |     at endReadableNT (_stream_readable.js:1220:12)
0|homebridge  |     at processTicksAndRejections (internal/process/task_queues.js:84:21)
0|homebridge  | .
0|homebridge  | [9/27/2020, 3:15:29 PM] [eWeLink] [TH16 Cozinha] requesting previous state to revert Homebridge st
