Bug 26785: Fix JS error in pos/pay.tt

Bug 26785: Fix JS error in pos/pay.tt

To Test:
1. enable  EnablePointOfSale
2. enable  UseCashRegisters
3. Go to /cgi-bin/koha/pos/pay.pl
4. See the console error
5. Apply patch
6. Add some debit types and make sure you can add them /cgi-bin/koha/pos/pay.pl
7. Check for console errors, there should be none
8. Make sure you can confrim payments.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>