Some feeds are not parsed by Aperture

Sometimes, Aperture reports that a feed contains 0 items when there are items.

Here are a few feeds for which this is a problem:

- https://winnielim.org/wp-json/wp/v2/pages/3040 (JSON Feed)
- https://schmud.de/pages/feeds.html (mf2 h-feed)
- https://winnielim.org/feed/ (RSS)