MQTT does not start if username and password left empty

[EpoxyRaisin]

If your mqtt-broker, like mine, does not utilize any authentication and you leave username and password empty in config.js, the connection to the mqtt-broker will not be enabled at all. That is because of:
const mqttEnabled = (config.mqtt.mqttBroker !== '') &&
(config.mqtt.username !== '') &&
(config.mqtt.password !== '') &&
(config.mqtt.machineName !== '')
in PeripheralManager.js

The quick fix for me was to insert some dummy values for username and password in config.js

[JaapvanEkris]

Good point. Although not advised to do that to a MQTT broker, it indeed is a valid approach on a home network. I'll loosen the restrictions a bit in the next release.