Bug 23432: Replace 'die' with 'warn'

Bug 23432: Replace 'die' with 'warn'

This patch simply replaced the die statement with a warn such that the
cron script may continue to rotate other items even if this item cannot
be properly rotated due to corrupt data.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 6adb1891d2bf602b0434eb87508568e73faa763e)

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