Update node_base.py

Fixes a bug in NodeItem.set_proxy_mode

Author: jlalleve-EA

NodeGraphQt/qgraphics/node_base.py

@@ -560,7 +560,7 @@ def set_proxy_mode(self, mode):
         visible = not mode
 
         for w in self._widgets.values():
-            w.widget.setVisible(visible)
+            w.widget().setVisible(visible)
         for port, text in self._input_items.items():
             port.setVisible(visible)
             if text.visible_: