Simpler API for creating CoreStore-managed NSFetchedResultsControllers, useful for external SDK's that require them

CoreStore/Internal/CoreStoreFetchedResultsController.swift

@@ -48,6 +48,10 @@ internal final class CoreStoreFetchedResultsController<T: NSManagedObject>: NSFe
     
     internal init<T>(context: NSManagedObjectContext, fetchRequest: NSFetchRequest, from: From<T>? = nil, sectionBy: SectionBy? = nil, fetchClauses: [FetchClause]) {
         
+        CoreStore.assert(
+            fetchClauses.filter { $0 is OrderBy }.count > 0,
+            "An \(typeName(NSFetchedResultsController)) requires an OrderBy clause."
+        )
         from?.applyToFetchRequest(fetchRequest, context: context, applyAffectedStores: false)
         for clause in fetchClauses {