[refactor] Fix error message in udpRegistration
[refactor] Fix error message in udpRegistration

TheThingsNetwork/ttn,mgranberry/ttn,mgranberry/ttn,jvanmalder/ttn,jvanmalder/ttn,TheThingsNetwork/ttn,LoRaWanSoFa/ttn,LoRaWanSoFa/ttn,jvanmalder/ttn,TheThingsNetwork/ttn,mgranberry/ttn