Bug 33716: (QA follow-up) Fix submission when cardnumber is invalid

Bug 33716: (QA follow-up) Fix submission when cardnumber is invalid

Issue that this patch fixes:
1) Enable ILLmodule and install FreeForm, run:
bash <(curl -s https://raw.githubusercontent.com/ammopt/koha-ill-dev/master/start-ill-dev.sh)
2) Copy the example YAML text into the system preference input box
3) Create a new FreeForm request and enter a duff borrowernumber e.g. '11111111111111'
4) Click 'Create'. Submit the type disclaimer stage.
5) Notice there's an error
6) Apply this patch.
7) Repeat steps 3 and 4. Verify that the correct 'The borrower details you entered are invalid' error message is displayed instead of the error in 5).

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>