Don't try to resolve state if native_value is Null (#67134)

homeassistant/components/wolflink/sensor.py

@@ -152,6 +152,7 @@ class WolfLinkState(WolfLinkSensor):
     def native_value(self):
         """Return the state converting with supported values."""
         state = super().native_value
+        if state is not None:
             resolved_state = [
                 item for item in self.wolf_object.items if item.value == int(state)
             ]