Notebook: fix passing can-close-tabs

Make sure can_close_tabs can be passed in as a keyword parameter (to be set
by the GObject constructor).

[split out from another patch]
Signed-off-by: Sascha Silbe <silbe@activitycentral.com>

src/sugar3/graphics/notebook.py

@@ -44,9 +44,8 @@ class Notebook(gtk.Notebook):
         #        Set the 'can-close-tabs' property using **kwargs
         #        Set True the scrollable notebook property
 
-        gobject.GObject.__init__(self, **kwargs)
-
         self._can_close_tabs = None
+        GObject.GObject.__init__(self, **kwargs)
 
         self.set_scrollable(True)
         self.show()