Error: Broken function concat

[wasm-forge]

The concat function is broken in version 0.10.16. It inserts a separator even for an empty list, see the example:

        let t = concat([1, 2].iter().map(|_x| RcDoc::text("2")), ",")
            .pretty(LINE_WIDTH)
            .to_string();

        println!("{t}");
        let t = concat([1].iter().map(|_x| RcDoc::text("1")), ",")
            .pretty(LINE_WIDTH)
            .to_string();

        println!("{t}");
        let v: Vec<u8> = Vec::new();
        let t = concat(v.iter().map(|_x| RcDoc::text("0")), ",")
            .pretty(LINE_WIDTH)
            .to_string();
        println!("{t}");

before it was producing:

2,
2,
1,

It now produces:

2,
2,
1,
,