Add nodes adds unnecessary nodes, breaks Number Nodes

[prkos]

Add nodes extension adds a node on top of the first node of the path, sometimes even three nodes appear stacked in the same place. It only happens over the first node.

This breaks Number Nodes extension if it's used after Add nodes which gives:

Traceback (most recent call last):
  File "dots.py", line 108, in <module>
    e.affect()
  File "/home/prkos/inkscapedev/9500/install/share/inkscape/extensions/inkex.py", line 215, in affect
    self.effect()
  File "dots.py", line 73, in effect
    self.separateLastAndFirst(p)
  File "dots.py", line 48, in separateLastAndFirst
    x = dx/dist
ZeroDivisionError: float division

[su_v (suv-lp)]

Duplicate of bug #202540 in Inkscape: “Modify path effects open closed paths” (comment #3 and later)?

[Alvin Penner (apenner)]

confirmed. running 0.48pre1, I get the Python crash only with closed paths, not open paths

[su_v (suv-lp)]

Attached to bug #202540 is a preliminary patch trying to solve the issue for current bzr builds. Would you object to mark this one as duplicate to #202540?