Grouped transform animation vanishes when a round-trip value starts from a float residue #3937

I ran into this while porting motion to svelte on top of motion-dom as an experiment, and I think it's a bug.

A looping y: [0, -18, 0] sometimes just vanishes in Chromium. When the grouped transform animation rebuilds mid-cycle, the first keyframe comes back as -1.9387e-30 instead of 0. getEasing only treats an exact 0 as "no change", so it divides by a range of ~1e-30 and you get:

keyframes: ["translateY(-1.9387e-30px)", "translateY(0px)"]
easing:    linear(0 0%, -5.4e+27 0.5%, ...)

Compositor just gives up and the element stops painting.

Quick repro since I can't submit a PR: didier@5742906

Essentially:

animate(element, { y: [0, -18, 0] }, {
    duration: 1.2,
    ease: "easeInOut",
    repeat: Infinity,
    repeatDelay: 0.9,
    delay: 0.66
})