Bug 14138: Patroncard: Warn user if PDF creation fails

Bug 14138: Patroncard: Warn user if PDF creation fails

Change patroncards/create-pdf.pl to redirect with an error message
instead of writing an invalid pdf that does not open in pdf viewer.

To test:
- Apply patch

- Test that pdf creator behaves as before (with valid batches and
  patron lists)

- While testing, copy pdf link address from window with title 'Click
  the following link(s) to download...'

- Open another staff client browser tab

- Paste link to browser address field, change batch id rsp. patron
  list id to an invalid value and submit

- The window should redirect to cgi-bin/koha/patroncards/create-pdf.pl
  and display an error message

- Bonus test 1: Create an empty patron list and test patron card
  creation. You should get an error message as appropriate.

- Bonus test 2: Use a link with params like the following:
  ...create-pdf.pl?borrower_number=61&template_id=2&layout_id=1&start_card=1
  Verify that you can create a pdf with a valid borrower_number and that
  you get the error message with an invalid borrower number

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>