[web/views/rdf] Take the second element of XY equivalent for non final relation When given a Yams snippet of the form `<etype> <rtype>` ``xy.xeq()`` will return the XML snippet equivalent to this relation in the form of a tuple `(subject, rtype, object)` so ``item`` will always be a tuple here. In fact, the correct code appears just a few lines above (around line 88) for final relations so I guess this is a copy-paste mistake. Closes #4745929.

for eschema in schema.entities():
    if not (eschema.final or 'cw_source' in eschema.subjrels):
        add_relation_definition(eschema.type, 'cw_source', 'CWSource', ask_confirm=False)

sql('INSERT INTO cw_source_relation(eid_from, eid_to) '
    'SELECT e.eid,s.cw_eid FROM entities as e, cw_CWSource as s '
    'WHERE s.cw_name=e.source AND NOT EXISTS(SELECT 1 FROM cw_source_relation WHERE eid_from=e.eid AND eid_to=s.cw_eid)')
commit()