A thermostat group shows 0°C as current temperature
A thermostat group shows 0°C as current temperature, while the individual thermostats contained in the group show the correct temperature.

Please see attached screenshot.

Homebridge 1.3.4 / homebridge-fritz-platform v6.0.14

![Fritz Thermostat Group](https://user-images.githubusercontent.com/34392542/126838437-6bb6c094-3bee-4361-9a2d-108b5a332d8c.png)
