TRV schedule names are being cleared

It appears there are a few topics that publish information about a thermostat. One appears to possibly not include information about schedules, so the plugin defaults to an empty list.

ShellyMQTT/ShellyMQTT.indigoPlugin/Contents/Server Plugin/Devices/Shelly_TRV.py

Line 120 in d0c6659

self.schedule_profile_names = thermostat.get("schedule_profile_names", [])

I think the default should be changed to None, and when a None value is read (the TRV should ways produce a list), the internal list should be left unchanged. If the TRV has its schedules cleared, then it would report an empty list which would then be replace in indigo.