now handles url-buttons correctly

[valentinomariotto]

Hi guys! I made this little modification so that the driver can use the API capability to make "url buttons". Buttons which open the user browser when clicked on. A feature sought-after by a lot of people.

I read your guide on contributing. Look, this is the first time I submit my code to an open project, I'm only a beginner, and I can hardly make sense of your requirements. I don't have time for this at the moment. Sorry. Just take a look below, it's pretty straightforward.

Thank you

[filippotoso]

I replaced !== with isset().

I'll write some tests to check it works correctly and then it will be merged.