TraversalHelper.replaceStep sets previousStep to the wrong step

    public static <S, E> void replaceStep(final Step<S, E> removeStep, final Step<S, E> insertStep, final Traversal.Admin<?, ?> traversal) {
        final int i;
        traversal.removeStep(i = stepIndex(removeStep, traversal));
        traversal.addStep(i, insertStep);
    }