pl.struct named expr combined with .name.keep() PanicException

[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.DataFrame({"x": [1]}).select(pl.struct(foo = pl.all().name.keep()))

Log output

thread '<unnamed>' panicked at crates/polars-plan/src/plans/conversion/expr_expansion.rs:549:79:
called `Result::unwrap()` on an `Err` value: InvalidOperation(ErrString("`keep`, `suffix`, `prefix` should be last expression"))

Issue description

Example doesn't really make sense - I had a misplaced .name.keep() call.

Expected behavior

No panic.

Installed versions

--------Version info---------
Polars:               1.0.0
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>

[cmdlineluser]

Fixed by #19196