[dataimport] fix db-namespace default value handling
In a fresh new instance, the "db-namespace" option is set as empty
by default in the "sources" file.
This seems correct but empty string is not a valid pg_schema and
actually means that we should use "public"
.. role:: raw-html(raw)
:format: html
RSS driven
----------
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href="../view?vid=rss&rql=Any+X%2CM+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30"><img
alt="rss" src="../data/rss.png"> latest changes</a></p>`