diff -r 3e2aebc9c7c0 -r 3e7bd88fcff7 editors/ConfTreeNodeEditor.py
--- a/editors/ConfTreeNodeEditor.py	Tue May 28 10:03:41 2013 +0200
+++ b/editors/ConfTreeNodeEditor.py	Tue May 28 17:52:07 2013 +0200
@@ -531,8 +531,8 @@
             if res != textctrl.GetValue():
                 if isinstance(textctrl, wx.SpinCtrl):
                     textctrl.SetValue(res)
-                else:
-                    textctrl.ChangeValue(res)
+                elif res is not None:
+                    textctrl.ChangeValue(str(res))
             if refresh:
                 wx.CallAfter(self.ParentWindow._Refresh, TITLE, FILEMENU, PROJECTTREE, PAGETITLES)
                 wx.CallAfter(self.ParentWindow.SelectProjectTreeItem, self.GetTagName())