[Vala] Getting Vala not to give a GValue pointer to a function?

[Faheem Pervez <trippin1 gmail com>]

Hiya,

Vala n00b here, so be nice, please.

The function http://maemo.org/api_refs/5.0/5.0-final/mafw/mafw-MafwMetadata.html#mafw-metadata-first
returns a GValue when given a a GHashTable and a string. That's all
well and good, except Vala also tries to give it a pointer to a GValue
as the third argument. As you can see, it only takes two arguments.

The relevant part of mafw.vapi looks like:
        [CCode (cheader_filename = "libmafw/mafw.h")]
        public static unowned GLib.Value metadata_first (GLib.HashTable md,
string key);

and I'm invoking it thus:
                unowned GLib.Value artist = metadata_first(metadata, "artist");
                unowned GLib.Value title = metadata_first(metadata, "title");
                unowned GLib.Value album = metadata_first(metadata, "album-art-uri");

Which produces the following C code:
        GValue _tmp0_ = {0};
        GValue artist;
        GValue _tmp1_ = {0};
        GValue title;
        GValue _tmp2_ = {0};
        GValue album;
        g_return_if_fail (self != NULL);
        g_return_if_fail (metadata != NULL);
        artist = (mafw_metadata_first (metadata, "artist", &_tmp0_), _tmp0_);
        title = (mafw_metadata_first (metadata, "title", &_tmp1_), _tmp1_);
        album = (mafw_metadata_first (metadata, "album-art-uri", &_tmp2_), _tmp2_);

and GCC exits with the following: error: too many arguments to
function 'mafw_metadata_first' [x3]

So, how can I make Vala not try and pass a GValue to the non-existent
third parameter of mafw_metadata_first and instead use the one given
to it by mafw_metadata_first? Thanks!

Best Regards,
Faheem