Scroll on Firefox 64.0

[Almostsk]

On Mozilla firefox, scroll working reversed.
Like i'm scroll down page go up.

[Artanisky]

@river-lee , This problem is still relevant.

[webistomin]

@river-lee, I have error on fullpage.js:238:17

console.log(e.wheelDelta); returns undefined

[firibz]

I have same problem,
On Mozilla Firefox, scroll working reversed.