don't break if "None" model is merged with others

fixed "copy" method for polygons (no lines were copied before)


git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@1153 bbaffbd6-741e-11dd-a85d-61de82d9cad9

src/pycam/Geometry/Model.py

@@ -70,6 +70,8 @@ def get_combined_bounds(models):
     return low, high
 
 def get_combined_model(models):
+    # remove all "None" models
+    models = [model for model in models if not model is None]
     if not models:
         return None
     result = models.pop(0).copy()

src/pycam/Geometry/Polygon.py

@@ -231,7 +231,10 @@ class Polygon(TransformableContainer):
         self._cached_offset_polygons = {}
 
     def copy(self):
-        return self.__class__(plane=self.plane.copy())
+        result = self.__class__(plane=self.plane.copy())
+        for line in self.get_lines():
+            result.append(line.copy())
+        return result
 
     def append(self, line):
         if not self.is_connectable(line):