[BUG] battery IO wrong when a sensor is unavailable

[Santobert]

Describe the bug
A clear and concise description of what the bug is.

My battery input sensor was unavailable for some time around midnight. At the morning it became available again and proceeded working as expected

The change from 'unavailable' to a number was shown by the card, while the original energy card correctly ignored it.

To Reproduce
Steps to reproduce the behavior:

1. Configure a sensor as the battery input
2. Set the sensor to any number
3. Set the sensor to 'unavailable'
4. Wait until the next morning
5. Set the sensor to the exact same number as in step 2
6. See that the card shows that number as a sudden battery charge, while the original energy card correct ignores that

Expected behavior
A clear and concise description of what you expected to happen.

Unavailable means that the last known value is correct, not zero.

Screenshots
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Desktop (please complete the following information):

• OS: android
• Browser: companion app
• Version 2023-10-2

Smartphone (please complete the following information):

• Device: pixel 6

Additional context
Add any other context about the problem here.

Please make sure all of this applies and check the checkboxes, by writing "X" inside of them.

• I understand that this is a channel for reporting bugs, not a support forum (If you need help configuring the card, go to: Discussions).

• I have the latest version of the card installed.

• I have cleared my browser cache after installing, updating and configuring the card.