Updated cadnano reader to work with recent pull of cadnano (ce6ff019)

dnarbd/readers/cadnano_segments.py

@@ -209,7 +209,11 @@ class cadnano_part(SegmentModel):
             # TODO add code to encode Parts with ARBITRARY point configurations
             raise NotImplementedError("Not implemented")
         else:
-            vh_props, origins = part.helixPropertiesAndOrigins()
+            try:
+                vh_props, origins = part.helixPropertiesAndOrigins()
+            except:
+                origins = {hid:part.getVirtualHelixOrigin(hid)[:2] for hid in part.getidNums()}
+
         self.origins = origins
 
         vh_list = []