判断代理是否为空

写代码一定要严谨，block一定要判断是否为空，代理虽然不用判断，但加上最好   

 if (self.delegate && [self.delegate respondsToSelector:@selector(CatorySelected:andItem:andIndex:)]) {        [_delegate CatorySelected:self andItem:button andIndex:button.tag];    }