Panic when converting dataframe to arrow

[coastalwhite]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

import polars as pl
import io
from hypothesis import given, settings
from polars.testing import assert_frame_equal
from polars.testing.parametric import dataframes

@given(df=dataframes(min_size=5, excluded_dtypes=[pl.Decimal, pl.Categorical]))
@settings(
    max_examples=100,
    deadline=None,
)
def test_parquet_pyarrow_write_roundtrip(df: pl.DataFrame) -> None:
    f = io.BytesIO()
    df.write_parquet(f, use_pyarrow=True)
    f.seek(0)
    assert_frame_equal(pl.read_parquet(f), df)

Log output

thread '<unnamed>' panicked at crates/polars-arrow/src/array/ffi.rs:64:24:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Issue description

There is a panic in the conversion to arrow. I am not really able to reproduce this outside of the parametric test, so I am leaving this for later.

Expected behavior

No panic.

Installed versions

Replace this line with the output of pl.show_versions(). Leave the backticks in place.

[pbower]

Hi there,

I'd like to report that I'm experiencing the same issue with the following details:

OrderedDict([('index_123e4567-e89b-12d3-a456-426614174000', UInt32), ('A', Object), ('B', Null), ('C', Null), ('D', Null), ('E', Null), ('F', Null), ('G', Null), ('H', Null), ('I', Null), ('J', Null), ('K', Null),...

Where 'A' object contains a nested struct like this :

The exact error message is:

Exception has occurred: PanicException
called `Option::unwrap()` on a `None` value
...
pyo3_runtime.PanicException: called `Option::unwrap()` on a `None` value

If you require any further information please let me know.

Regards,
PB