Bug 19692: fix unclosed div in opac-shelves.tt

Bug 19692: fix unclosed div in opac-shelves.tt

Test plan:
1. set syspref OpacKohaUrl to "Show"
2. Log into the OPAC
3. /cgi-bin/koha/opac-shelves.pl
4. Notice that "Powered by Koha" is not in the footer in this page.
  When on the other tabs it's in the footer (out of .main)
5. Apply this patch
6. Notice that "Powered by Koha" now in the footer in the "your lists" page

Signed-off-by: Dominic Pichette <dominic@inlibro.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 30f2b40f3c408a1f81eae57c5012e6283eccb3d0)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>