how can i push the RKSwipeBetweenViewControllers in a uinavigationviewcontroller

[holyen]

when i push the object of RKSwipeBetweenViewControllers
it crash.
code:
RKSwipeBetweenViewControllers *swipeVC = [RKSwipeBetweenViewControllers newSwipeBetweenViewControllers];
[nav_tweet.viewControllerArray addObjectsFromArray:@[[TimelineViewController newTimelineViewControllerWithType:TimelineViewControllerType_Nearby],
[TimelineViewController newTimelineViewControllerWithType:TimelineViewControllerType_Hot]]];
nav_tweet.buttonText = @[@"A", @"B"];
[self.navigationController pushViewController:nav_tweet animated:YES];

then it crash log is : NSScanner: nil string argument
how to fix it ?