Bug 16747 - Patron card creator broken with version 16.05

Bug 16747 - Patron card creator broken with version 16.05

To reproduce:
- Prepare a patron car layout with Image 1 using Patron Image
- Create a patron card for a patron without patron image
Result: OK, PDF can be opened wit PDF viewer
- Try to create a patron card with a patron who has a patron image
Result: The PDF file is corrupt (contains text only with error message)
        intranet error log contains: create-pdf.pl: Illegal division
        by zero at /usr/share/kohaclone/patroncards/create-pdf.pl line 200
To test:
- Apply patch
- Create a patron card with a patron who has a patron image
Result: PDF is OK and contains the image

Bonus test: Do the same with a card layout with an additional image
(Image 2: Image source: Other image)

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Test and bonus test pass: PDF generated without errors.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>