隐藏admob插页式广告后留空白空间？

Question

点击插页式广告上的隐藏按钮后，屏幕底部会出现大约50px的空白空白，我无法检测到导致这种情况的原因 这是我用来请求和查看插页式广告的代码，有关如何解决它的任何想法？

    - (void)webViewDidFinishLoad:(UIWebView*)theWebView
{
    interstitial_ = [[GADInterstitial alloc] init];
    interstitial_.adUnitID = @"XXXXXXXXXXXXXXXXXXXXXX";
    interstitial_.delegate = self;
    GADRequest *request = [GADRequest request];
    request.testDevices = @[                         
                            GAD_SIMULATOR_ID,
                            ];

    [interstitial_ loadRequest:request];
    return [super webViewDidFinishLoad:theWebView];
}


- (void)interstitialDidReceiveAd:(GADBannerView *)adView {
    [interstitial_ presentFromRootViewController:self];
}