Bug 18734 - Internal server error in cash_register_stats.pl when exporting to file

Bug 18734 - Internal server error in cash_register_stats.pl when exporting to file

To test:
Output cash reigster stats report to file
Internal server error
Apply patch
Export to file
File is generated and correctly formed

Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 855ff0fb9a1cf7755a0805910c367150b37b5f2a)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
(cherry picked from commit 8e1cfdbd07bf0dceab147ab5df417d7deedaada8)
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>