fixed rare extrusion bug (triggered by multiple identical vertices in a triangle)

git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@1250 bbaffbd6-741e-11dd-a85d-61de82d9cad9

src/pycam/Geometry/Model.py

@@ -934,7 +934,10 @@ class PolygonGroup(object):
                         final_points.append(cp)
         else:
             final_points.extend([Point(*coord) for coord in coords])
-        valid_points = [p for p in final_points if not p is None]
+        valid_points = []
+        for p in final_points:
+            if not (p is None) and not (p in valid_points):
+                valid_points.append(p)
         if len(valid_points) < 3:
             result = []
         elif len(valid_points) == 3: