Check for nil port value and only append if present

Sometimes I don't know the port number of the host -- or we're just using the default protocol port.  Instead of trying to determine the appropriate port number I'd like to leave it up to the protocol to pick the default port if I don't set one explicitly.  This pull request checks to ensure a port value was supplied and only then appends it to the URL.  Otherwise "(null)" is included in the url string.