Creating a series of empty structs produces a series of a single item

[universalmind303]

Polars version checks

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Issue description

creating a series of empty structs returns an invalid result, and regardless of the number of empty items, it will always produce a series with exactly 1 item.

related to #6148

Reproducible example

use polars::prelude::*;

fn main() {
    let dtype = DataType::Struct(vec![]);
    let structs = vec![AnyValue::StructOwned(Box::new((vec![], vec![]))); 3];
    let s = Series::from_any_values_and_dtype("", &structs, &dtype).unwrap();
    assert_eq!(s.len(), 3);
}

Expected behavior

I'd expect the series to have the same length of the input vec.

Installed versions

polars = {git = "https://github.com/pola-rs/polars.git", branch = "master", features = ["dtype-full"]}