Bug 22807: Ensure only one maincontent on searcresults

Bug 22807: Ensure only one maincontent on searcresults

Prior to this patch, if you entered a search that returned zero results,
you would end up with two 'maincontent' classes on the page

Signed-off-by: Hayley Mapley <hayleymapley@catalyst.net.nz>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 6b0887f76e2f561187f6eae78f932987520a9cb6)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>