`Batch::send(self)` hangs when batch is empty

Hi ! Thanks a lot for your amazing work, your crate has been very helpful so far.

I found what I believe to be a bug, it is so simple, yet it took me an hour or so to figure this out.

I build a batch of Netlink messages based of various inputs, and in some rare cases nothing will be written to it. When that happens, my program hangs.

It's a shame that I have to create intermediate Vecs just to call is_empty() on them before calling Batch::send(self).

I guess something as simple as that would be enough ?

if self.buf.is_empty() {
    return Ok(());
}

Minimal reproducible example:

fn main() {
    let batch = rustables::Batch::new();
    batch.send().unwrap();
}

(must be run as root otherwise it will fail successfully)