sudden crash. cause unknow.

```

Noble Fates Critical Error:

NullReferenceException: Object reference not set to an instance of an object

ItemActor.Land (System.Boolean audio) (at <f853eae5cb7c44c8b8e1fa7144bd65d3>:0)

ItemActor.Tick (System.Single dt) (at <f853eae5cb7c44c8b8e1fa7144bd65d3>:0)

ItemManager.Tick (System.Single dt) (at <f853eae5cb7c44c8b8e1fa7144bd65d3>:0)

ManagerBehavior.Update () (at <f853eae5cb7c44c8b8e1fa7144bd65d3>:0)

```