[entity] fix fetch_rql w/ case where it's called while entity is not 'complete' (eg time where it's being added but have not yet all mandatory relations set)
""" CW - nevow/twisted client
:organization: Logilab
:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
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:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
"""