Sortable Problem - can't drop item into an empty ul

Sortable Problem - can't drop item into an empty ul


Hello,
I'm trying to realize a sortable treeview with nested lists. In the
first place everything seems to work fine, but then I realized once a
list is empty - I can't drop an element inside again. I prepared a
little demo for that:
http://www.9elements.com/projects/draganddrop/
Any fixes? Any tipps? Any workarounds?
Cheers
Sebastian
ps: I already tried to make an unmovable element, so that the list
will never be empty. I also have tried to give the list a min-height.
Both ways did not work.