RSS feed template errors when there are no posts

[cbirdsong]

Used this as the basis for an extremely simple documentation site, and noticed the template filter rssLastUpdatedDate does not handle an empty collections.posts gracefully. Sidestepping the error is pretty simple:

{% if collections.posts | length %}
  <updated>{{ collections.posts | rssLastUpdatedDate }}</updated>
{% endif %}

However, I'm new to Eleventy, and this may need to be accompanied by a lower-level way to simply not output the RSS feed at all if there are no posts to fill it with.