Do not hand out libxml2-allocated strings
Do not hand out libxml2-allocated strings

We can't use xml_util_get_child_element_content_glib as this early-exits and
we need to collect all values that can occur.

On top of that, don't add empty list entries.

https://bugzilla.gnome.org/show_bug.cgi?id=708751

GNOME/gupnp,GNOME/gupnp,GNOME/gupnp,GNOME/gupnp