Return empty Much() when encountering an unknown class

Author: bouwew

plugwise/helper.py

@@ -253,7 +253,7 @@ def _appliance_info_finder(self, appl: Munch, appliance: etree.Element) -> Munch
                 appl.zigbee_mac = module_data["zigbee_mac_address"]
                 return appl
             case _:  # pragma: no cover
-                return appl
+                return Munch()
 
     def _appl_gateway_info(self, appl: Munch, appliance: etree.Element) -> Munch:
         """Helper-function for _appliance_info_finder()."""