[bug] Weight API: `bodyfat` and `measurement` are set to `0` on update

[cyroxx]

Steps to reproduce

1. Create (POST) a weight record via the API with bodyfat and measurement set to null.
2. Verify that in the Health app, this is actually created with bodyfat and measurement set to null.
3. Update (PUT) that same weight record via the API with bodyfat and measurement set to null.

Expected behavior

bodyfat and measurement should still be null after the update.

Actual behavior

bodyfat and measurement were set to 0 (zero) after the update.

Health app version

2.2.2

Additional info

No response

[cyroxx]

This is somewhat related to #146.

[maxi1134]

Could you let me know how you post the data?

I get CSRF check failed at every try