.struct.field('*') PanicException when used after .list.to_struct()

[cmdlineluser]

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

pl.select(pl.lit('a.b.c').str.split('.').list.to_struct().struct.field('*'))

Log output

thread '<unnamed>' panicked at crates/polars-plan/src/logical_plan/conversion/expr_expansion.rs:362:22:
index out of bounds: the len is 0 but the index is 0

Issue description

I'm not sure if this can actually work in a single context due to .list.to_struct() having an "unknown schema".

But the PanicException can be fixed.

Using a separate context works as expected.

>>> pl.select(pl.lit('a.b.c').str.split('.').list.to_struct()).select(pl.all().struct.field('*'))
shape: (1, 3)
┌─────────┬─────────┬─────────┐
│ field_0 ┆ field_1 ┆ field_2 │
│ ---     ┆ ---     ┆ ---     │
│ str     ┆ str     ┆ str     │
╞═════════╪═════════╪═════════╡
│ a       ┆ b       ┆ c       │
└─────────┴─────────┴─────────┘

Expected behavior

No panic exception.

Installed versions

--------Version info---------
Polars:               1.0.0-beta.1
Index type:           UInt32
Platform:             macOS-13.6.1-arm64-arm-64bit
Python:               3.12.2 (main, Feb  6 2024, 20:19:44) [Clang 15.0.0 (clang-1500.1.0.2.5)]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          <not installed>
connectorx:           <not installed>
deltalake:            <not installed>
fastexcel:            <not installed>
fsspec:               <not installed>
gevent:               <not installed>
great_tables:         <not installed>
hvplot:               <not installed>
matplotlib:           <not installed>
nest_asyncio:         <not installed>
numpy:                1.26.4
openpyxl:             <not installed>
pandas:               2.2.1
pyarrow:              15.0.2
pydantic:             <not installed>
pyiceberg:            <not installed>
sqlalchemy:           <not installed>
torch:                <not installed>
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>