Bug 37411: Fixed 500 error when exporting budget planning

Bug 37411: Fixed 500 error when exporting budget planning

To test:
1. Acquistions -> Budgets -> Funds -> Planning, select any option
2. In the toolbar see Export, and click Submit and see a 500 error
3. Apply patch, restart_all
4. Repeat steps 1-2
5. Notice the 500 error is gone and the CSV is exported properly

Notes:
Is there a reason we call exit(1) after exporting the csv?

Signed-off-by: Roman Dolny <roman.dolny@jezuici.pl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>