保存过滤的FetchedResults时CoreData崩溃

context.performAndWait {
    do {
        try context.save()
    } catch {
        print("Failed to save context: \(error)")
    }
}

if fetchedResultsController.fetchedObjects?.count > 0 {
    do {
        try context.save()
    } catch {
        print("Failed to save context: \(error)")
    }
}

let backgroundContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
backgroundContext.parent = context

backgroundContext.perform {
    // Perform operations on backgroundContext
    do {
        try backgroundContext.save()
        context.performAndWait {
            do {
                try context.save()
            } catch {
                print("Failed to save main context: \(error)")
            }
        }
    } catch {
        print("Failed to save background context: \(error)")
    }
}