Menu editor tree is not in sync with backend after a deeply nested menuitem is collapsed & expanded again

Steps to reproduce:

1. Go to channel manager in edit mode
2. Go to menu editor
3. Select "news" menu item.
4. add a new menu item(eg.test1)
5. make (Test1) child of "news" menu item by sliding it to the right.
6. now select(Test1) and create new menu item(eg.Test2)
7. Make (Test2) child of (Test1) by sliding it to right
8. Now collapse (Test1) and then "news" menu item
9. Expand "news" menu-item.
10. Notice is removed from (Test1) child menu item and there is no (Test2) menu item which was child of (Test1) menu-item

So above behaviour should be fixed