by reloading current lines before adding a brand new one
indeed the info are deleted by ClearCustomProperties
each time SfxDocumentInfoItem destructor is called

Change-Id: Id1e2e652e90c720f00b8612aa9afbfa91b784d1d
Reviewed-on: https://gerrit.libreoffice.org/50070Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>
Reviewed-on: https://gerrit.libreoffice.org/51297Reviewed-by: Jean-Baptiste Faure <jbfaure@libreoffice.org>
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>
(cherry picked from commit 5d3313c8)