Fix infinite loop in traversing function.

Filters/Modeling/vtkContourLoopExtraction.cxx

@@ -96,7 +96,7 @@ namespace {
     // Recall that we are working with 2-pt lines
     while ( !terminated )
     {
-      last = pts[1];
+      last = (pts[0]!=last ? pts[0] : pts[1]);
       numInserted++;
       t = dir * static_cast<double>(numInserted);
       sortedPoints.push_back(LoopPoint(t,last));