SearchRaw & .FacetItems Throw Exception w/ Latest Commit

The following line is now generating an exception because `this.Infer` is null for `.SearchRaw` calls:

```
        public IEnumerable<F> FacetItems<F>(Expression<Func<T, object>> expression) where F : FacetItem
        {
            var fieldName = this.Infer.PropertyPath(expression);
            return this.FacetItems<F>(fieldName);
        }
```
