g_vasprintf crashes when passed invalid UTF-8

https://gitlab.gnome.org/GNOME/glib/-/blob/main/glib/gprintf.c#L365

g_printf_string_upper_bound return less then 1 len

g_new alloced NULL

len = _g_vsprintf (*string, format, args2); used NULL *string

at finally crashed

i propose solution

gsize nsize = g_printf_string_upper_bound (format, args);
if (nsize < 1)
{
    *string = NULL;
    return nsize;
}
*string = g_new (gchar, nsize);