With the recent changes in diplomacy, it can happen that AI players can become neutral with each other in-game, but if these players defeat the last enemy player renaming,
then they will stay neutral indefinitely, and no player(s) will have "won" (regardless of the gamesetup option allied victory / last man standing option). There should be only an early return in lastManStandingCheck if AlliedVictory and if the player has allies. Also, there should be an early return when teams are locked.
While at it, rename diplomacyRequests to receivedDiplomacyRequests, to match with sentDiplomacyRequests.