fix: use dict.get with default empty

Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>

DDG4/python/DDSim/DD4hepSimulation.py

@@ -357,9 +357,8 @@ class DD4hepSimulation(object):
          (self.action.stack, DDG4.StackingAction, kernel.stackingAction)]:
       for action_dict in action_list:
         action = DDG4_Action(kernel, action_dict["name"])
-        if 'parameter' in action_dict.keys():
-          for parameter, value in action_dict['parameter'].items():
-            setattr(action, parameter, value)
+        for parameter, value in action_dict.get('parameter', {}).items():
+          setattr(action, parameter, value)
         kernel_Action().add(action)
 
     # ----------------------------------------------------------------------------------