Проверка, является ли imageView пустым.
if ([imageView isEqual:nil]) {
//if the image view is empty do the following
NSLog(@"imageView:%@ is empty", imageView);
}else{
//If the image view is not empty do the following
NSLog(@"imageView:%@ is not empty", imageView);
//For example, in viewDidLoad, you could set UIImageView as nil
[imageView setImage:nil];
}