Bug 10215: (follow-up) Correct existing data

Bug 10215: (follow-up) Correct existing data

This patch adds the correction of data ('' => NULL) during the DB
update.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 9713e13893c9f2d2b12cea29b23b72a25170462e)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
(cherry picked from commit 648587b19c7e8ca4a91b9930c7d6c78fbeb2da0f)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>