Objective c can not catch exception from calling super method-Collection of common programming errors

I am calling a super method from my subclass. But sometimes the object of the superclass (UIWindow) is nil so it will fail. I try to catch the exception but it doesn´t work. The app still crashes. Can anyone tell me why and how I can fix this?

- (void)sendEvent:(UIEvent *)event;  
{
     @try {
         [super sendEvent:event];
     }
     @catch(NSException *e) {
         NSLog(@"%@",e);
         return;
}

Thanks a lot