Alternative to #618. Fixes #616. This behavior is more consistent with how rects treat insets, e.g.,

I’d slightly prefer using the midpoint here, something like:

if (right >= left) {
  scale.range = [left, right];
} else {
  const center = (right + left) / 2;
  scale.range = [center, center];
}

But then I’d want rects to behave similarly, and I don’t think it’s really worth the trouble for such a rare thing. Mostly I just want to avoid the surprising (to me) behavior of the scale’s range getting inverted when the insets or margins are too big, and I think a collapsed range is a sufficient indication of a misconfiguration and we don’t need to do more.