Bug 12210 - Baker & Taylor book jackets not disabled when BakerTaylorBookstoreURL...

Bug 12210 - Baker & Taylor book jackets not disabled when BakerTaylorBookstoreURL is not populated

The description of the BakerTaylorBookstoreURL syspref says
"Baker and Taylor "My Library Bookstore" links should be accessed at
https://   isbn (this should be filled in with something like
ocls.mylibrarybookstore.com/MLB/actions/searchHandler.do?nextPage=bookDetails&parentNum=10923&key=).
Leave it blank to disable these links."

Leaving this syspref blank does not disable the links. Instead, they are
populated without the bookstore URL: the cover image for ISBN 1575725738
will cause koha to make a request to http://1575725738, which will, of
course, time out.

Leaving BakerTaylorBookstoreURL blank should disable any URL that
depends on this syspref, as stated in the syspref description.

Test Plan:
1) Apply this patch
2) Enable Baker & Taylor cover images, but *not* BakerTaylorBookstoreURL
3) Perform an OPAC search where you have B&T cover images in the results
4) Note the image links now direct you to the record details

Signed-off-by: Sheila Kearns <sheila.kearns@state.vt.us>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Only affects Baker & Taylor related parts of the code.
Read the code carefully, but couldn't test in the OPAC.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>