`warp::body::content_length_limit` rejects requests without `Content-Length` and `Transfer-Encoding`

[heinrich5991]

This is also documented as such: warp::body::content_length_limit. I use warp 0.3.2, but the documentation didn't change since then.

According to hyperium/hyper#3633, if both Content-Length and Transfer-Encoding are missing, it means that the body is empty. I'd expect such a request to not be rejected by the content_length_limit filter.