message: validate footer element exists before applying style
diff: @@ -171,7 +171,9 @@ export const useTechDocsReaderDom = (entityRef: EntityName): Element | null => {
  const updateFooterWidth = useCallback(() => {
  if (!dom) return;
  const footer = dom.querySelector('.md-footer') as HTMLElement;
  + if (footer) {
  footer.style.width = `${dom.getBoundingClientRect().width}px`;
  + }
  }, [dom]);
  useEffect(() => {
  