Quest items can be transferred to a corpse which subsequently gets deleted

... soft-locking the player.

Fixing this is going to be tricky because we can't use `npc:object(section)` in `release_body_manager.try_to_release()` since some corpses may be on another level and hence won't have a client entity (`npc`) available. That means the solution will probably have to involve keeping track of whether there are quest items on a corpse via a flag on the server entity.