In some circumstances, which I am finding extremely hard to reproduce, NS tree returns an object twice.
If model Foo is a subclass of NS_Node, the query on the default manager Foo.objects.all() will return the first object twice, as the first and last object in the query (always).
Surprisingly, Foo.objects.filter() sometimes behaves appropriately and does not return any object twice, other times its output is identical to the problematic all().
This bug will only manifest after delete or move operations have been performed (i.e. even after tens of thousands of node creations, I have not witnessed it).
