set secnode target to '' on disconnect

devices.py

@@ -643,10 +643,14 @@ class FrappyNode(SecNodeDevice, Moveable):
             self._cache.put(self, 'value', cfg)
         self._setROParam('target', cfg)
 
+    def _disconnect(self):
+        super()._disconnect()
+        self.target = ''
+
     def get_info(self):
         result = self.doRead() or ''
         code, text = self.status()
-        if not result and self.target and self._secnode:
+        if not result and self.target:
             return '<disconnected>'
         if code == status.OK or result == '':
             return result