fix ci

hysop/simulation.py

@@ -448,6 +448,8 @@ class Simulation:
             io_params = kwds.pop('io_params')
         _params = ()
         for p in params:
+            if p is None:
+                continue
             for (_, param) in p.iterviews():
                 _params += (param,)
         params = _params