code: @Nullable
      private static View getEmptyView(@Nullable View rootView) {
          if (rootView == null) {
              throw new RuntimeException("A null rootView was passed to getEmptyView, but Hits/RefinementList require one.");
          }
          return rootView.findViewById(android.R.id.empty);
      }
docs: Finds the empty view in the given rootView.
  
  @param rootView the topmost view in the view hierarchy of the Activity.
  @return the empty view if it was in the rootView.
  @throws RuntimeException if the rootView is null.