If you look at the URL provided, you'll see at the top that it's trying to kick off the subpage navigation due to the presence of a slash in the title. However, there is no existing parent pages for this to be a subpage of, as the title has a leading slash. Basically, articles with leading slashes shouldn't kick the subpage navigation.
Version: 1.11.x
Severity: minor
URL: http://en.wikipedia.org/wiki/Talk:/dev/null