wxStaticBoxSizer and wizard.py produce GTK warnings

Hello,

If using StaticBoxSizers in the wx wizard demo, I get alot of:

(python:13110): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to
allocate widget with width -2 and height 15

warnings. You can try this for yourself by adding:

box = wx.StaticBox(self, -1, 'Test')
bsizer = wx.StaticBoxSizer(box, wx.VERTICAL)
self.sizer.Add(bsizer)

to the init method of class UseAltBitmapPage. I'm running wx-2.8 on Ubuntu
Gutsy Gibbon.

Regards,
Frank