Bug 17886: Don't show option to add to existing list if there are no lists

Bug 17886: Don't show option to add to existing list if there are no lists

This patch modifies the page for adding a title to a list so that the
"Add to existing list" option doesn't appear if there are no lists
defined.

TEST PLAN
---------
1) Make sure no lists exist at all.
2) Make there is at least one findable biblio record entered
3) Find that biblio record in the OPAC
4) Click 'Save to your lists'
   -- Notice that the whole save to list section is there.
5) Apply this patch
6) Click 'Cancel'
7) Click 'Save to your lists'
   -- Notice you can only add now, which makes sense.
8) Run koha qa test tools.

Perform the same tests in the staff client.

Signed-off-by: Maryse Simard <maryse.simard@inlibro.com>
Followed the test plan and the patch works.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit b6010314dfed0f35c87de1a6c8209cd3e8f8b3c8)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>