tableview滑动后DZNEmptyDataSet 消失或者

更改源码为下面的方法：

• (void)didMoveToSuperview
  {
  CGRect frame = self.superview.bounds;
  frame.origin.y = 0;
  self.frame = frame;

  void(^fadeInBlock)(void) = ^{_contentView.alpha = 1.0;};

  if (self.fadeInOnDisplay) {
  [UIView animateWithDuration:0.25
  animations:fadeInBlock
  completion:NULL];
  }
  else {
  fadeInBlock();
  }
  }