It becomes even crazier if there is no valid country. The Game bugs out, the HRE window disappears and every day the tag "REB" gets elected emperor. In the imperial mapmode the sahara then becomes ligh green as if it where a player.Apparently this is what happens when you vassalize all the electors, stay a Republic and cause havoc in the current Emperor's country right before he dies. He's succeeded by an African minor.
Strangest part is that, while Mutapa was converted at some point, it hadn't expanded beyond its starting boundaries and was still a Tribal Federation.