Fixed logic error in CountItemsUnder() that would sometimes
return the wrong count. This would result in issues such as
Vision's network reordering failing to reorder down due to
retrieving the wrong item based on the count.
This fixes ticket #2447.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@26149 a95241bf-73f2-0310-859d-f6bbb57e9c96