With autoindex disabled, going to an existing dir that does not have an
index.html will generate a 403 Forbidden error.  There should be a friendly
page rather than a blank white default page. For example, this works:

https://f-droid.org/wp-content/uploads/2016/06/downloaded-updates.png
https://testy.at.or.at/wp-content/uploads/2016/06/downloaded-updates.png

This does not:

https://testy.at.or.at/wp-content/uploads/2016/06/
https://f-droid.org/wp-content/uploads/2016/06/