Adjust type hint in meteoalarm (#77818)

homeassistant/components/meteoalarm/binary_sensor.py

@@ -74,15 +74,14 @@ class MeteoAlertBinarySensor(BinarySensorEntity):
         self._attr_name = name
         self._api = api
 
-    def update(self):
+    def update(self) -> None:
         """Update device state."""
-        self._attr_extra_state_attributes = None
+        self._attr_extra_state_attributes = {}
         self._attr_is_on = False
 
         if alert := self._api.get_alert():
             expiration_date = dt_util.parse_datetime(alert["expires"])
-            now = dt_util.utcnow()
 
-            if expiration_date > now:
+            if expiration_date is not None and expiration_date > dt_util.utcnow():
                 self._attr_extra_state_attributes = alert
                 self._attr_is_on = True