message: transport: fix empty buffer parsing for tls hello messages
diff: @@ -462,10 +462,12 @@ impl<Config: endpoint::Config> InitialSpace<Config> {
  let mut chunks = crypto_stream.iter().peekable();
  let buffer = s2n_codec::DecoderBuffer::new(chunks.peek().unwrap_or(&&[][..]));
  - let (header, _) = buffer.decode::<tls::HandshakeHeader>().map_err(|_| {
  - transport::Error::PROTOCOL_VIOLATION
  - .with_reason("initial crypto is missing hello header")
  - })?;
  + let header = if let Ok((header, _)) = buffer.decode::<tls::HandshakeHeader>() {
  + header
  + } else {
  + // we don't have enough data to parse the header so wait until later
  + return Ok(None);
  + };
  if header.msg_type() != Some(msg_type) {
  return Err(transport::Error::PROTOCOL_VIOLATION
  