do not complain when no output module is configured

frappy/mixins.py

@@ -71,8 +71,11 @@ class HasOutputModule:
 
     def initModule(self):
         super().initModule()
+        try:
             if self.output_module:
                 self.output_module.register_input(self.name, self.deactivate_control)
+        except Exception:
+            self.log.info(f'{self.name} has no output module')
 
     def set_control_active(self, active):
         """to be overridden for switching hw control"""