guzzle/guzzle — pull request #504 by ethangui (2013-12-20 20:37:22+00:00)
Title: allows '0' to be the request body

Since PHP treats '0' as false, therefore, we will skip setting the body value if $body=='0'.

I suppose this is not the intended behavior as the request body can theoretically be '0'.

Changed condition to be not null.