<!doctype html>
<title>Attempting to resolve a font-relative (em) SVGLength in a detached document does not crash</title>
<iframe></iframe>
<script>
  const rect = document.createElementNS("http://www.w3.org/2000/svg", "rect");
  rect.setAttribute("height", "16em");
  const iframe = document.querySelector('iframe');
  iframe.contentDocument.documentElement.appendChild(rect);
  iframe.remove();
  rect.height.baseVal.value;
</script>
