I keep getting the error "uncaught exception: Cannot tween a null target." when hovering one of the buttons in this codepen demo i've created, the animation is applied to a pseudoelement, and it looks all correct to me. The second button in the demo works, but the first doesn't for some reason. Originally the two buttons were different, one with the styling i wanted to apply alongside the animation, but i kept getting this exception, so i chipped away at all the additional styling and animations until i was left with this bug. The markup, js and styling is practically identical, except with a different classname and id for the elements. Does anyone know why this would be happening? Thank you!