Fix detection of if a negative node is in use (#11255)

* Fix detection of if a negative node is in use

Fix a problem where every negative node gets detected as in-use. Code was not checking the correct property.

* Allow protected access

homeassistant/components/binary_sensor/isy994.py

@@ -165,7 +165,8 @@ class ISYBinarySensorDevice(isy.ISYDevice, BinarySensorDevice):
         """
         self._negative_node = child
 
-        if not _is_val_unknown(self._negative_node):
+        # pylint: disable=protected-access
+        if not _is_val_unknown(self._negative_node.status._val):
             # If the negative node has a value, it means the negative node is
             # in use for this device. Therefore, we cannot determine the state
             # of the sensor until we receive our first ON event.