Error creating PredicateDescription

   Hi kpinniger,
The bug for this has been fixed. To clarify, the bug fix for this is a clearer exception message rather than a null ref exception. 

Below is the correct way to build a predicate with a null item in the list.

var list = new short?[] { 0, 1, 2, 3 }.ToList();
var p = new PredicateDescription(typeof(Product), Product.EntityPropertyNames.UnitsInStock, FilterOperator.InList, list);
var p2 = new PredicateDescription(typeof(Product), Product.EntityPropertyNames.UnitsInStock, FilterOperator.IsEqualTo, null)
var p3 = p.Or(p2);
var q = EntityQuery.Create(typeof(Product)).Where(p3);