Bug 27715: (QA follow-up) Remove conditional declaration

Resolves:
FAIL critic # Variables::ProhibitConditionalDeclarations: Got 1 violation(s).

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

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

C4/Utils/DataTables.pm

@@ -116,8 +116,7 @@ sub dt_build_orderby {
       push @sanitized_orderbys, "$sanitized_identifier $sanitized_direction";
     }
 
-    my $orderby = " ORDER BY " . join(',', @sanitized_orderbys) . " " if @sanitized_orderbys;
-    return $orderby;
+    return " ORDER BY " . join(',', @sanitized_orderbys) . " " if @sanitized_orderbys;
 }
 
 =head2 dt_get_params