ComputeError( "...The column is already aggregated.")

[AnatolyBuga]

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• I have confirmed this bug exists on the latest version of Polars.

Issue description

Hello Team Polars,

This issue might be related to 4978.

This was not the case with 0.23.x In this example I would expect ColumnNotFound Error. But instead I get this:

ComputeError(
        Owned(
            "Cannot aggregate as sum. The column is already aggregated.",
        ),
    ),

Reproducible example

pub fn issue(){

    let mut df1 = df![
        "a" => ["a", "b", "c", "a", "d"],
        "b" => [true, false, true, true, true],
        "c" => [Some(1), None, Some(3), Some(4), Some(5)]
    ].unwrap(); 

    dbg!(df1.lazy().groupby([col("a"), col("b"), col("c")])
        .agg([
            example().sum().alias("new_name")]).collect());
}

pub(crate) fn example () -> Expr {

    apply_multiple(
        move |columns| {
            let df = df! [
                "d" => &columns[0],
                "e" => &columns[1],
                "f" => &columns[2]
            ]?;
            let res = df.column("noSuchColumn")?;
            Ok(res.to_owned())
        },
        &[
            col("a") ,
            col("b"),
            col("c"),
        ],
        GetOutput::from_type(DataType::Float64),
    )
}

Expected behavior

Column Not Found Error

Installed versions

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