Work around possible HTTP::Tiny issue timing out for receiving empty bytes from the servers.

Don't attempt to print empty bytes ('') in the test suite. It used to
work fine with LWP::UserAgent as a client, but causes timeout with
HTTP::Tiny clients for local sockets.

https://github.com/chansen/p5-http-tiny/issues/21
https://github.com/stash/Feersum/issues/14