Added hiding fix

If you used selecter with scroller and scroll list by mouse (click, hold and drag scroll-bar), after scrolling selecter was hiding if cursor not on scroll-bar. But if change .parents in _onCloseHelper to .closest this bug is fixed. 

Now list is not hiding if cursor on list (not only on scroll-bar) after scrolling.

before pull request: https://www.screenr.com/ZykN
after pull request: https://www.screenr.com/kykN