Hi,
I put that in "Feature request" but it really looks buggy to me... here are the steps to see it:
- Add items in a multiple values nodereference field via the "Add another item button"
- Leave one slot empty and then continue to fill the next ones
- Save the node
- Edit the node again : the empty slots are still here.

=> I can't see the utility in keeping the empty slots. And when the user who edit is not the user who created the node, the edit form looks weird...
What do you think of filling the empty slots with the next referenced node - offset everything so there is no more empty slots in the next edit?