Bug 26137: Remove warnings from viewlog.pl

Bug 26137: Remove warnings from viewlog.pl

The warnings are
Use of uninitialized value $val in concatenation (.) or string at /kohadevbox/koha/C4/Templates.pm line 138.
Problem = a value of  has been passed to param without key at /kohadevbox/koha/C4/Templates.pm line 138.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 8b541714a177fc141c77967c8fc528c5c5453139)

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