[gtkmm] output of Glib::PropertyProxy<Gtk::Color>

[Anton Sodja <asodja email si>]

In code which outputs setting file is such a function:

void TSettings::out_color(const Gdk::Color &cl) {
  out.fill('0');
  out << std::hex << std::setw(2) << (cl.get_red() % 0x100)
      << std::hex << std::setw(2) << (cl.get_green() % 0x100)
      << std::hex << std::setw(2) << (cl.get_blue() % 0x100) << std::dec
      << std::flush;
  out.fill(' ');
}

In my code, this method is called like that:
if (style_tag && style_tag->property_foreground_set()) {
    // ...
    out_color(style_tag->property_foreground_gdk().get_value());
}

Output is fine, but I get such warning:
(hc11asm-gui:8239): GLib-GObject-WARNING **: gvalue.c:86: cannot 
initialize GValue with type `GdkColor', the value has already been 
initialized as `GdkColor'

I don't know how to get rid of that message. I try to search google, but 
 with no success.
What am I supposed to do?

lp,
Anton