Change state() to try/except to catch KeyError (#19935)

* Change state() to try/except to catch KeyError

When Tautulli is up but Plex is down, the API doesn't return a 'stream_count' key. This causes calls to state() to raise KeyError exceptions. The new code includes a try/except to catch the KeyError and return -1 signifying that the Tautulli API cannot talk to Plex

* Update tautulli.py

homeassistant/components/sensor/tautulli.py

@@ -119,7 +119,7 @@ class TautulliSensor(Entity):
     @property
     def state(self):
         """Return the state of the sensor."""
-        return self.sessions['stream_count']
+        return self.sessions.get('stream_count')
 
     @property
     def icon(self):