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>
(cherry picked from commit 7367b114c916aab9bebd06135fe889cf2a8883d4)
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit 1adce64d84fbd2f082e11786e9f5dd533f9ba6c3)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>