在解除导航弹出窗口后，共享的iAd横幅会卸载广告

I saw a few other similar questions but could find any answers... I have a shared iAd banner. The problem is when I load it in a modally presented NavigationController with a TableViewController, when I dismiss the TableViewController the Ad Banner in the MainViewController loses the ad and I receive the following error:I saw a few other similar questions but could f