wed fix

Really simple fix.  Check at least 2 nodes.  The current failure occurs because the node checked has incidence 2 and is a member of the set of nodes that bounds a region.  By checking at least one other node in the filament we know that it is either internal to the region or external to the region.  The minimum size of a filament will be 2, so we know that the check will never fail due to an insufficient number of nodes in the filament.

I *think* that this should be less expensive than either of our original solutions.  Mine requires an additional if check before we set the pointers.  Serge's requires a call to enumerate the links around the node.