characteristic 'Temperature Display Units': characteristic value expected valid finite number and received "undefined" (undefined)
Plugin version 3.6.22

Using callback just with one argument "temperatureDisplayUnits" causes warning.
I'm not sure about my proposal but maybe it's correct to use **callback(null, temperatureDisplayUnits)** in aircon.js file

https://github.com/lprhodes/homebridge-broadlink-rm/blob/21b4ceb0b1ca87406ab8dfa7fa33cf19b5ce2cee/accessories/aircon.js#L563

**Warning logs:**
[9/15/2021, 3:23:03 PM] [homebridge-broadlink-rm] This plugin generated a warning from the characteristic 'Temperature Display Units': characteristic value expected valid finite number and received "undefined" (undefined).
[9/15/2021, 3:23:03 PM] [homebridge-broadlink-rm] Error
    at TemperatureDisplayUnits.Characteristic.characteristicWarning (/usr/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Characteristic.js:1242:41)
    at TemperatureDisplayUnits.Characteristic.validateUserInput (/usr/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Characteristic.js:1145:26)
    at /usr/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/Characteristic.js:758:55
    at /usr/lib/node_modules/homebridge/node_modules/hap-nodejs/dist/lib/util/once.js:18:25
    at AirConAccessory.getTemperatureDisplayUnits (/usr/lib/node_modules/homebridge-broadlink-rm/accessories/aircon.js:563:5)

After update to **callback(null, temperatureDisplayUnits);** no more warnings from plugin.