A separator as the last (sub)menu entry gets drawn on top of the first menu entry.
This is in most cases just cosmetic and simply removing an "unused" separator from the bottom of the menu fixes it, but it really should work properly instead.
Reported in IRC for a few times already, so it seems like a fairly usual problem for people.
Added the patch to git.
Please test the attached patch for any regressions and if it does actually fix the issue. Thanks!