Deal with Creatures being deleted before a battle they're part of.

Signed-off-by: Deukhoofd <Deukhoofd@gmail.com>

src/Battling/Models/BattleSide.cpp

@@ -54,7 +54,7 @@ void BattleSide::SetCreature(ArbUt::OptionalBorrowedPtr<Creature> creature, uint
     if (old.HasValue()) {
         old.GetValue()->SetOnBattleField(false);
     }
-    _creatures[index] = creature.GetValue();
+    _creatures[index] = creature;
     if (!creature.HasValue()) {
         return;
     }