fixed engraving for 2D models (remaining migration issue):

* Closed: http://sourceforge.net/tracker/?func=detail&aid=3441481&group_id=237831&atid=1104176


git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@1219 bbaffbd6-741e-11dd-a85d-61de82d9cad9

src/pycam/Plugins/ProcessStrategies.py

@@ -172,7 +172,7 @@ class ProcessStrategyEngraving(pycam.Plugins.PluginBase):
                 tool=tool, models=environment["collision_models"])
         path_generator = pycam.PathGenerators.EngraveCutter.EngraveCutter(
                 pycam.PathProcessors.SimpleCutter.SimpleCutter())
-        models = list(process["parameters"]["trace_models"])
+        models = [m.model for m in process["parameters"]["trace_models"]]
         if not models:
             self.log.error("No trace models given: you need to assign a " + \
                     "2D model to the engraving process.")