Why empty destructor in gtkmm HelloWorld example?

[Francesco Pretto <ceztkoml gmail com>]

Hello, can someone explain me what's the rule of the empty ~HelloWorld()
destructor in gtkmm Hello World example[1]? Actually base class
Gtk::Window destructor would be called anyway, whatever ~HelloWorld()
is defined or not, and it's not clear to me if it's just a redundant
statement, a convention or something that's really needed by gtkmm to
proper deallocate memory.

Thanks,
Francesco

http://library.gnome.org/devel/gtkmm-tutorial/unstable/sec-helloworld.html.en