I have next code

```
if (user != null)
  query = query.Where(item => item.User.Id == user.Id);
else if (equipment != null)
  query = query.Where(item => false);// TODO: Add logic for equipment

```

but NHibernate can't build expression tree for `item => false`. Someday this expression will change, but now it must return empty query. Is there some method to solve this problem?