Fix Gamepad handling when only one axis is present

[sherpal]

... in particular, a single connected Joy-Con.

Fixes https://github.com/PurpleKingdomGames/indigo/issues/760

I imagine we could go one step further and handle the hypothetical case where there is 0 axis (They seem to exist*). But as I don't own one, I can't verify whether it would actually translate to the axes array to be of length 0. So I would leave it like that for now.