Panic crash with assertion failed in Polars 1.17.0 scratch.is_empty()

[coby-astsec]

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

col = pl.col("A")
# Only crashes with a LazyFrame
df = pl.LazyFrame([{"A": "1/1"}])

# This step is required for the crash, if I just build a df with an already split element it will not crash
df = df.with_columns(
    col.str.split("/")
)

# Just using `df.with_columns(col.list.get(0))` is not enough to crash
df = df.with_columns(
    pl.when(
        col.is_not_null()
    ).then(
        # Crash is here? Changing this to `None` stops the crash
        col.list.get(0)
    ).otherwise(
        None
    )
)

# This line will crash because of laziness
print(df.collect())

Log output

❯ POLARS_VERBOSE=1 uv run test.py
thread '<unnamed>' panicked at crates/polars-plan/src/plans/optimizer/slice_pushdown_lp.rs:52:5:
assertion failed: scratch.is_empty()
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Traceback (most recent call last):
  File "/path/to/test.py", line 20, in <module>
    print(df.collect())
          ~~~~~~~~~~^^
  File "/path/to/.venv/lib/python3.13/site-packages/polars/lazyframe/frame.py", line 2031, in collect
    return wrap_df(ldf.collect(callback))
                   ~~~~~~~~~~~^^^^^^^^^^
pyo3_runtime.PanicException: assertion failed: scratch.is_empty()

Issue description

Code that worked with Polars 1.16.0 has stopped working with 1.17.0
I'm not quite sure what the crash is, only that there has to be a very specific set of steps to cause the crash.
The reproduction is short and commented.

Expected behavior

No crash, print:

shape: (1, 1)
┌─────┐
│ A   │
│ --- │
│ str │
╞═════╡
│ 1   │
└─────┘

Installed versions

--------Version info---------
Polars:              1.17.0
Index type:          UInt32
Platform:            macOS-15.1.1-arm64-arm-64bit-Mach-O
Python:              3.13.0 (main, Oct  7 2024, 23:47:22) [Clang 18.1.8 ]
LTS CPU:             False

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