The signal is deprecated, and the handler is only helping for a really tiny corner case anyway. https://bugzilla.gnome.org/show_bug.cgi?id=734961
Normally, a GtkAboutDialog is shown using the convenience API. But if you manually construct one and show it by calling gtk_widget_show_all() on it, the license tab would show up uninvited. Fix that. https://bugzilla.gnome.org/show_bug.cgi?id=724411