iOS8 iPad Warning: Attempt to present <UIImagePickerController:xxxx > on xxxx which is already presenting (null)

/*
     I think this is because in iOS 8, alert views and action sheets are actually presented view controllers
     (UIAlertController). So, if you‘re presenting a new view controller in response to an action from the UIAlertView, 
     it‘s being presented while the UIAlertController is being dismissed.I worked around this by delaying the 
     presentation of the UIImagePickerController until the next iteration of the runloop, by doing this:
*/
__weak typeof(self) weakSelf = self;
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
    [weakSelf presentViewController:imagePicker animated:YES completion:nil];
}];