Bug 20068: Check if user logged in before passing dashboard params to template

Bug 20068: Check if user logged in before passing dashboard params to template

This prevents warns from dashboard variables when not logged in

To test:
1) Go to OPAC main homepage. Do not log in
2) Notice warn
3) Apply patch and refresh
4) Warn should be gone
5) Log in
6) Confirm dashboard shows as normal

Sponsored-by: Catalyst IT
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>