issue 156, avoid PHP 7.4 Notice (array offset on value of type int)

[ennorehling]

This should fix issue #156 - $port is an integer, and there is no reason to access it as an array or string.

I noticed there is no test for this, and don't know how to create one. Also, the UnirestRequestTest::testGzip test seems to be failing, but it already did that before my change.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}