Fix enigma2 off state (#42407)

homeassistant/components/enigma2/media_player.py

@@ -133,6 +133,11 @@ class Enigma2Device(MediaPlayerEntity):
             return STATE_PLAYING
         return STATE_OFF if self.e2_box.in_standby else STATE_ON
 
+    @property
+    def available(self):
+        """Return True if the device is available."""
+        return self.e2_box.is_offline
+
     @property
     def supported_features(self):
         """Flag of media commands that are supported."""