Return nan instead of 0 for temp when aircon is offline

[camsaway]

Is your feature request related to a problem? Please describe.
When graphing temperature or looking in history for Midea AC Outdoor Temperature it shows 0 when the aircon is offline.

Describe the solution you'd like
I would prefer it to return not available / no value rather than 0. I feel this is a more accurate reflection of the true value

Describe alternatives you've considered
Create a template sensor to "hide" this behaviour.

Additional context
Through my smart home, I disconnect power to the aircon units when the battery storage is running low and the solar forecast is not good. I don't just power off the unit.