Fix joyride error

Hi,

Because of #5511, when the joyride is included on the page but hasn't been started yet (with `$(document).foundation('joyride', 'start')` not called on page load but manually),
the keystrokes events are still catched and we end up with a JS error.

This fix checks that the joyride is on screen before calling theses callbacks.

Thanks, and sorry for the error !