Prevent using a bad tree item.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@37633 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

wxPython/wx/py/filling.py

@@ -159,6 +159,8 @@ class FillingTree(wx.TreeCtrl):
 
     def display(self):
         item = self.item
+        if not item:
+            return
         if self.IsExpanded(item):
             self.addChildren(item)
         self.setText('')