Bug 24736: Disable "Enrollments" link if nobody enrolled to the club yet

Bug 24736: Disable "Enrollments" link if nobody enrolled to the club yet

The link is disabled but it's possible to click and access the page
anyway.

Test plan:
- Create a new club template
- Create a new club
- Click the Actions > Enrollments link
=> Without this patch you can access the page
=> With this patch applied you cannot, and a tooltip explains why (feel
free to suggest another wording)
- Add a new patron to this club (from /cgi-bin/koha/opac-user.pl#opac-user-clubs)
- Notice that the action link is not enabled and click takes you to the
list of enrollments

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>