fix(sensor): Add safe guards for missing coordinator data in KACO integration

[MIKOLAJW197]

Issue

Custom KACO integration crashes when coordinator.data["extra"] is None.
This caused sensors not to be added and TypeError exceptions in the logs.

Solution

• Added safe access to extra data in unique_id and device_info.
• Provided fallback values for serialno and model to prevent crashes.
• Sensors will now load even if the API response is incomplete or missing extra.

Tests

• Verified sensors are created with fallback values.
• No errors in logs when extra is missing.

[KoljaWindeler]

Hi, thanks for your work, I see the same behavior that the entity is not getting loaded when no data are received and always wanted to fix this.
Testing your changes leads to multiple entities (one with serial nr and one without for me) do you see the same?

[MIKOLAJW197]

For me with this code I am seeing one entity
But if there is an issue on your end, I may rethink the solution

[KoljaWindeler]

I'll also spend some time today and playaround with chatgpt :D

[KoljaWindeler]

I've played around some time and chatGPT suggested to do many many changes .. honestly .. I've only tested the result .. once with disconnected inverter and once with .. both worked fine .. so this is at least better :)

[MIKOLAJW197]

@KoljaWindeler You messed something up :D
now in new version config-flow for edit don't work