Add some safety checks for property access in NMBS sensor (#33695)

homeassistant/components/nmbs/sensor.py

@@ -152,6 +152,10 @@ class NMBSLiveBoard(Entity):
     def update(self):
         """Set the state equal to the next departure."""
         liveboard = self._api_client.get_liveboard(self._station)
+
+        if liveboard is None or not liveboard["departures"]:
+            return
+
         next_departure = liveboard["departures"]["departure"][0]
 
         self._attrs = next_departure
@@ -266,6 +270,9 @@ class NMBSSensor(Entity):
             self._station_from, self._station_to
         )
 
+        if connections is None or not connections["connection"]:
+            return
+
         if int(connections["connection"][0]["departure"]["left"]) > 0:
             next_connection = connections["connection"][1]
         else: