fix(Statemachine): 在子弹过滤中添加实例有效性检查

确保在过滤子弹时检查实例是否有效，避免因无效实例导致的错误

scripts/Statemachine/CycleTimer.gd

@@ -17,7 +17,7 @@ func getStateAngle(index: int):
 func forceFilter():
 	bullets = bullets.filter(
 		func(b):
-			if b is BulletBase:
+			if is_instance_valid(b) && b is BulletBase:
 				return !b.destroying
 			else:
 				return false