[gupnp-av] Fix compile error with recent glib

[Jens Georg <jensgeorg src gnome org>]

commit ddca90752bd13a3ca01c868c034ade7b42408f52
Author: Jens Georg <mail jensge org>
Date:   Thu Oct 25 10:26:40 2018 +0200

    Fix compile error with recent glib

 libgupnp-av/gupnp-media-collection.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/libgupnp-av/gupnp-media-collection.c b/libgupnp-av/gupnp-media-collection.c
index f55ed41..0b4427e 100644
--- a/libgupnp-av/gupnp-media-collection.c
+++ b/libgupnp-av/gupnp-media-collection.c
@@ -89,7 +89,7 @@ on_container_available (GUPnPMediaCollection   *self,
         if (self->priv->container != NULL)
                 g_object_unref (self->priv->container);
 
-        self->priv->container = g_object_ref (container);
+        self->priv->container = GUPNP_DIDL_LITE_OBJECT (g_object_ref (container));
 }
 
 static void