NSFetchedResultsController returning 0 sections in Xcode 8.1, worked in 8.0

My app builds a table view using an NSFetchedResultsController to pull from Core Data. In Xcode 8, my table view was working fine; however, upon updating to Xcode 8.1, and without changing any code, the results controller seems to be no longer pulling results from Core Data.

I am not getting any error messages or warnings.

Results in debug look like:

-----------------------------------

(lldb) po fetchedResultsController

▿ Optional<NSFetchedResultsController>

(lldb) p fetchedResultsController

(NSFetchedResultsController<NSManagedObject>?) $R1 = 0x00006000000eda00 {

ObjectiveC.NSObject = {}

}

(lldb) p fetchedResultsController.fetchedObjects

([NSManagedObject]?) $R2 = 0 values

-----------------------------------

In a CoreDataTableViewController.swift parent class, the initializers for the fetched results controller:

    var fetchedResultsController: NSFetchedResultsController<NSManagedObject>! {
        didSet {
            fetchedResultsController.delegate = self
            executeSearch()
            tableView.reloadData()
        }
    }

    init(fetchedResultsController frc: NSFetchedResultsController<NSManagedObject>, style : UITableViewStyle = .plain) {

            fetchedResultsController = frc

            super.init(style: style)
    }

In the RouteTableVeiwController.swift subclass, the initialization of the fetched results controller:

  let request: NSFetchRequest<Route> = Route.fetchRequest()
  let routeTypeSort = NSSortDescriptor(key: "route_type", ascending: true)
  let routeShortNameSort = NSSortDescriptor(key: "route_short_name", ascending: true)
  request.sortDescriptors = [routeTypeSort, routeShortNameSort]

  let mainContext = CoreDataStack.shared.persistentContainer.viewContext

  let routeTableFetchedResultsController: NSFetchedResultsController<Route> =
  NSFetchedResultsController(fetchRequest: request,
                             managedObjectContext: mainContext,
                             sectionNameKeyPath: "route_type",
                             cacheName: nil)

  fetchedResultsController = routeTableFetchedResultsController as! NSFetchedResultsController<NSManagedObject>

And, executeSearch():func executeSearch(){

  do{
    try fetchedResultsController.performFetch()
    // also tried this:
    // try (fetchedResultsController as! NSFetchedResultsController<Route>).performFetch()
  }
  catch { ... }