Filter out transient attributes from fetchRequest propertiesToFetch: 

Need to filter out transient attributes from fetchRequest.propertiesToFetch or it will throw an exception "defaultValue (null)) passed to setPropertiesToFetch: (entity mismatch)". This is because transient attributes aren't actually created at the data level, they're calculated at run-time. The Core Data programming guide alludes to this: "You cannot fetch using a predicate based on transient properties"