fix: fix coredata crash on primary course (#64) (openedx#518)

Co-authored-by: Saeed Bashir <sbashir@2u.com>

OpenEdX/Data/DashboardPersistence.swift

@@ -231,7 +231,7 @@ public class DashboardPersistence: DashboardPersistenceProtocol {
     // swiftlint:enable function_body_length
 
     func clearOldEnrollmentsData() {
-        context.perform {[context] in
+        context.performAndWait {[context] in
             let fetchRequest1: NSFetchRequest<NSFetchRequestResult> = CDDashboardCourse.fetchRequest()
             let batchDeleteRequest1 = NSBatchDeleteRequest(fetchRequest: fetchRequest1)