Possible Glib::ustring::compose issue in gtkmm 2.22

[Guillaume Brocker <guillaume brocker digital-trainers com>]

Hi !

I've just started to migrate my projects to gtkmm2.22 and I found a 
possible issue using Glib::ustring::compose. Here is a little test case:

 Glib::ustring::compose( "%1", 123456 ); // Works
 Glib::ustring::compose( "%1", "Hello world" ); // Raises an exception


So the second line raises an exception and writes the following message 
to the console :

 unhandled exception (type Glib::Error) in signal handler:
 domain: g_convert_error
 code  : 0
 what  : Conversion from character set 'WCHAR_T' to 'UTF-8' is not 
supported


After little debugging, the error occurs in 
glibmm-2.24.2/glib/glibmm/ustring.cc at line 2182 and I'm using VC2008.

Thanks for your help.
Guillaume