message: Fix occasional panic when visiting settings.html
  Closes
diff: @@ -311,8 +311,13 @@ fn path_for_version(req_path: &[&str], target_name: &str, conn: &Connection) ->
  .expect("paths should be of the form <kind>.<name>.html")
  };
  // check if req_path[3] is the platform choice or the name of the crate
  + // rustdoc generates a ../settings.html page;
  + // if we get this far and we're on settings.html, there is no module.
  + // additionally, if settings.html doesn't exist on the most recent page,
  + // the build must have failed, so we just redirect to the root page.
  let concat_path;
  - let crate_root = if req_path[3] != target_name {
  + let crate_root = if req_path[3] != target_name && req_path[3] != "settings.html" {
  + assert!(req_path.len() >= 5, "{:?}", req_path);
  concat_path = format!("{}/{}", req_path[3], req_path[4]);
  &concat_path
  } else {
  