When viewport is changed, infinteGrid is not append automatically

[sculove]

Description

When viewport is changed, infiniteGird change viewport size in order to fit wrapper height of contents.
Therefore, when scroll event is fired, prevScroll position is larger than current scroll position.
infiniteGrid fire 'prepend' event. it's bug!!!

Steps to check or reproduce

1. scroll down and down (appended)
2. scroll down and down (appended)
3. scroll down and down (appended)
4. change resize or rotate!!!
5. you can see stopped contents of infiniteGrid.