NSInternalInconsistencyException This NSPersistentStoreCoordinator has no persistent stores

Question

I am initializing my model. If the local DB does not exists then I query my back end server to retrieve data and store in the core data (the first if statement). But I get the "NSInternalInconsistencyException This NSPersistentStoreCoordinator has no persistent stores" exception when I try to save (i.e. [self.gameDB saveToURL:self.gameDB.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL])

- (void)setUpGameModel
{

    if (!self.gameDB) {
        NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
        url = [url URLByAppendingPathComponent:@"GameDatabase"];
        self.gameDB = [[UIManagedDocument alloc] initWithFileURL:url];
    }

    if (![[NSFileManager defaultManager] fileExistsAtPath:[self.gameDB.fileURL path]]) {
       // does not exist on disk, so create it

        dispatch_queue_t fetchQ = dispatch_queue_create("New Game Fetcher", NULL);

        dispatch_async(fetchQ, ^{
            [self.gameDB.managedObjectContext performBlock:^{ // perform in the NSMOC's safe thread (main thread)
                [Game queryGameFromServerWithLevel:@"1" inManagedObjectContext:self.gameDB.managedObjectContext];
                [self.gameDB saveToURL:self.gameDB.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL];
            }];
        });

    } else if (self.gameDB.documentState == UIDocumentStateClosed) {
    // exists on disk, but we need to open it
        [self.gameDB openWithCompletionHandler:^(BOOL success) {
           [Game queryGameWithLevel:@"1" inManagedObjectContext:self.gameDB.managedObjectContext];
        }];
    } else if (self.gameDB.documentState == UIDocumentStateNormal) {
        // already open and ready to use
        [Game queryGameWithLevel:@"1" inManagedObjectContext:self.gameDB.managedObjectContext];
    }

}