I think this happened because in all the chaos on this turn KIENMAYER had no divisions allocated to him. Now I have allocated divisions all is back to normal, so the 'Division by 0' message is probably not a game 'system' warning, but a 'game-play' message.
Because of the format of the message it looked like a bug warning, but it's maybe just part of the game, in which case it should look more like the other game message panels.
"In politics stupidity is not a handicap" - Napoleon
“A people which is able to say everything becomes able to do everything” - Napoleon
“Among those who dislike oppression are many who like to oppress" - Napoleon