Creating frames with List(Struct(...Categorical)) fails depending on order

[billylanchantin]

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
dtype = pl.datatypes.List(pl.datatypes.Struct({"field": pl.datatypes.Categorical()}))
pl.DataFrame({"col": [[], [{"field": "example"}]]}, schema={"col": dtype})

Log output

thread '<unnamed>' panicked at /Users/runner/work/polars/polars/crates/polars-arrow/src/array/binview/mod.rs:336:9:
assertion failed: i < self.len()
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/path/to/.venv/lib/python3.12/site-packages/polars/dataframe/frame.py", line 1182, in __repr__
    return self.__str__()
           ^^^^^^^^^^^^^^
  File "/path/to/.venv/lib/python3.12/site-packages/polars/dataframe/frame.py", line 1179, in __str__
    return self._df.as_str()
           ^^^^^^^^^^^^^^^^^
pyo3_runtime.PanicException: assertion failed: i < self.len()

Issue description

Creating the dataframe can fail when the first element of a List(Struct(...Categorical)) is an empty list.

Expected behavior

The data for this dataframe is valid, so creating it should succeed. If we swap the order of the inner list so the [] is no longer the head of the list, it actually does succeed:

pl.DataFrame({"col": [[{"field": "example"}], []]}, schema={"col": dtype})
# shape: (2, 1)
# ┌─────────────────┐
# │ col             │
# │ ---             │
# │ list[struct[1]] │
# ╞═════════════════╡
# │ [{"example"}]   │
# │ []              │
# └─────────────────┘

Installed versions

--------Version info---------
Polars:              1.14.0
Index type:          UInt32
Platform:            macOS-12.5-x86_64-i386-64bit
Python:              3.12.3 (v3.12.3:f6650f9ad7, Apr  9 2024, 08:18:48) [Clang 13.0.0 (clang-1300.0.29.30)]
LTS CPU:             False

----Optional dependencies----
adbc_driver_manager  <not installed>
altair               <not installed>
boto3                <not installed>
cloudpickle          <not installed>
connectorx           0.3.3
deltalake            <not installed>
fastexcel            <not installed>
fsspec               <not installed>
gevent               <not installed>
google.auth          2.34.0
great_tables         <not installed>
matplotlib           <not installed>
nest_asyncio         <not installed>
numpy                2.1.0
openpyxl             <not installed>
pandas               2.2.3
pyarrow              17.0.0
pydantic             <not installed>
pyiceberg            <not installed>
sqlalchemy           2.0.36
torch                <not installed>
xlsx2csv             <not installed>
xlsxwriter           <not installed>