Categorical column in points element becomes filled with `NaN`s

[LucaMarconato]

To reproduce: https://github.com/giovp/spatialdata-sandbox/blob/main/xenium_2.0.0_io/to_zarr.py

The problem is caused by

spatialdata/src/spatialdata/models/models.py

Line 894 in fe5fae7

data[c] = data[c].cat.set_categories(data[c].head(1).cat.categories)

.

Related to #1009 and could share the same fix proposed in #1010.

[LucaMarconato]

This shows the root of the problem:

[LucaMarconato]

It's indeed due to the same bug. In the next screenshot see the expected result (first command) and what we get in the code (second command).

[LucaMarconato]

I'll continue the discussion in #1010.