message: Add test for deleted index entry
diff: @@ -581,7 +581,6 @@ impl Summaries {
  return Poll::Ready(Ok(cached_summaries));
  }
  LoadResponse::NotFound => {
  - debug_assert!(cached_summaries.is_none());
  if let Err(e) = fs::remove_file(cache_path) {
  if e.kind() != ErrorKind::NotFound {
  log::debug!("failed to remove from cache: {}", e);
  