Bug 25526: Equality matching is case sensative

Bug 25526: Equality matching is case sensative

TEST PLAN:
1. Have a fine on a Patron's account.
2. Choose the "Write off Selected" button
3. Enter an amount less than the amount owed by the patron.
4. Koha will give a yellow box with a note "You must collect a value
   greater than or equal to 2.00." The $2.00 is the amount that is
   attempted to write off (the amount less than the amount owed).
5. Apply patch
6. Again try to writeoff an amount less than the amount owed.
7. You should be able to write it off.
8. Try paying an amount more than owed, you should still get an
   error. You shouldn't be able to write off more than the amount.
9. Follow the above steps via 'Pay selected' as aposed to 'Writeoff
   selected'.
10. You should not be able to 'Tender' less than the amount you have
    'Paid'.
11. Disable Javascript and run through all the above steps. You should
    still be blocked where relevant.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>