Parquet nested slice pushdown gives incorrect results

[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
from polars.testing import assert_frame_equal

df = pl.DataFrame({
    'a': [{ 'x': "" }, { 'x': "0" }],
})

df.write_parquet('/tmp/t.parquet')
df2 = pl.scan_parquet('/tmp/t.parquet').slice(1, 1).collect()

assert_frame_equal(df, df2)

Log output

Traceback (most recent call last):
  File "/home/johndoe/Projects/polars/py-polars/polars/testing/asserts/frame.py", line 114, in assert_frame_equal
    _assert_series_values_equal(
  File "/home/johndoe/Projects/polars/py-polars/polars/testing/asserts/series.py", line 182, in _assert_series_values_equal
    raise_assertion_error(
  File "/home/johndoe/Projects/polars/py-polars/polars/testing/asserts/utils.py", line 12, in raise_assertion_error
    raise AssertionError(msg) from cause
AssertionError: Series are different (exact value mismatch)
[left]:  [{'x': '0'}]
[right]: [{'x': ''}]

Issue description

Nested parquet structures don't interact well with tail slice pushdown.

Expected behavior

This should give the same output.

Installed versions

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