crash when using to_list() on list[extension] type series

[phc27x]

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

The following will crash a python kernel - verified with polars 1.11 on google colab.

import polars as pl
class PyO:
    def __init__(self, v):
        self._v = v       
    def __repr__(self):
        return f'PyO({self._v})'

df = pl.DataFrame( {'group':['A','B','A','C','B','C'],
               'value' : [ PyO(1), PyO(2),PyO(3), PyO(4), PyO(5), PyO(6)],
              }).group_by('group').agg( pl.col('value') )
srs = df['value']

srs.to_list()

Log output

keys/aggregates are not partitionable: running default HASH AGGREGATION

Issue description

A crash occurs when using to_list() on a polars series which has a dtype of list[extension] because it contains lists of python objects. The repro is short and reliable for creating a crash.

Maybe relevant observation: there are some other issues open relating to crashes when using extension type or python objects and they may have a common root cause to investigate.

Expected behavior

Expect that to_list() will get a list of lists of python objects.
The rendering as a polars series is the following:

And expectation is that to_list() should return

# if PyO.__eq__ is implemented
assert srs.to_list() == [[PyO(4), PyO(6)],[PyO(1), PyO(3)],[PyO(2), PyO(5)]] 

This expectation is consistent with how polars behaves in the repro, if using integers, instead of python objects:

assert srs_no_pyo.to_list() == [[4, 6], [1, 3], [2, 5]]

Installed versions

--------Version info---------
Polars:              1.11.0
Index type:          UInt32
Platform:            Linux-6.1.85+-x86_64-with-glibc2.35
Python:              3.10.12 (main, Sep 11 2024, 15:47:36) [GCC 11.4.0]
LTS CPU:             False

----Optional dependencies----
adbc_driver_manager  <not installed>
altair               4.2.2
cloudpickle          3.1.0
connectorx           <not installed>
deltalake            <not installed>
fastexcel            <not installed>
fsspec               2024.6.1
gevent               <not installed>
great_tables         <not installed>
matplotlib           3.7.1
nest_asyncio         1.6.0
numpy                1.26.4
openpyxl             3.1.5
pandas               2.2.2
pyarrow              16.1.0
pydantic             2.9.2
pyiceberg            <not installed>
sqlalchemy           2.0.36
torch                2.5.0+cu121
xlsx2csv             <not installed>
xlsxwriter           <not installed>

[cmdlineluser]

Can reproduce.

pl.DataFrame({'a': pl.DataFrame}).group_by(1).all()['a'].to_list()
# Segmentation fault: 11