Hotfix/Safeguards for device number properties

[FeliGoblin]

Proposed change:

User was getting a TypeError when VolumeConverter was trying to convert value None

  File "/usr/src/homeassistant/homeassistant/util/unit_conversion.py", line 131, in <lambda>
    return lambda val: (val / from_ratio) * to_ratio
                        ~~~~^~~~~~~~~~~~
TypeError: unsupported operand type(s) for /: 'NoneType' and 'float'

The change adds a safeguard to a bunch of device properties that should return numbers. Before, they only checked if the value exists, now it checks that it's a number.

For example:

    @property
    def today_feeding_quantity(self) -> int:
        return self._data.get("grainStatus", {}).get("todayFeedingQuantity", 0)

becomes:

    @property
    def today_feeding_quantity(self) -> float:
        quantity = self._data.get("grainStatus", {}).get("todayFeedingQuantity")
        return quantity if isinstance(quantity, (int, float)) else 0

Closes #183 (issue)

Type of change:

• New device.
• Bug fix (non-breaking change which fixes an issue).
• New feature or enhancement (non-breaking change which adds functionality).
• Documentation only.
• Other (please explain).

Checklist:

• If applicable, I have added corresponding documentation changes.
• If applicable, I have reviewed the feature / enhancement guidlines before submitting my request.
• If applicable, I have tested my code for new features & regressions on the latest version of Home Assistant.

Additional notes:

[jjjonesjr33]

Looks good, nice hot fix @FeliGoblin