Fixes invalid pointers to a battle dangling when a battle is removed.

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

src/Battling/Models/Creature.hpp

@@ -105,6 +105,7 @@ namespace CreatureLib::Battling {
         inline uint32_t GetCurrentHealth() const noexcept { return _currentHealth; }
 
         void SetBattleData(const ArbUt::BorrowedPtr<Battle>& battle, const ArbUt::BorrowedPtr<BattleSide>& side);
+        void ClearBattleData() noexcept;
         const ArbUt::OptionalBorrowedPtr<Battle>& GetBattle() const;
         const ArbUt::OptionalBorrowedPtr<BattleSide>& GetBattleSide() const;
         inline void SetOnBattleField(bool value) { _onBattleField = value; }