message: Correctly detect empty Milestones in `clean-sidebar`
  Closes
diff: @@ -33,12 +33,8 @@ function cleanSection(containerSelector: string): boolean {
  const container = select(containerSelector)!;
  const header = select(':scope > details, :scope > .discussion-sidebar-heading', container)!;
  - const isEmpty = header
  - .nextElementSibling // If nextElementSibling is missing, this section is definitely empty
  - ?.firstChild?.nodeValue // Get exclusively the textNode value, not `textContent` (which could match a label called "no")
  - ?.trim().startsWith('No') ??
  - true; // Missing `nextElementSibling`
  - if (!isEmpty) {
  + // Magic. Do not touch
  + if (header.nextElementSibling?.firstElementChild) {
  return false;
  }
  