Ticket #19567: patch-traitsbackendwx_helper.py.diff

enthought/traits/ui/wx/helper.py

@@ -413 +413 @@
             This method overrides the original in the base class so that
             nested subpanels are handled correctly.
         """
+        if child is None:
+            return
+
         sppux, sppuy = self.GetScrollPixelsPerUnit()
         vsx, vsy     = self.GetViewStart()