Bug 26032: (follow-up) Replace IFNULL() mysqlism with COALESCE()

Signed-off-by: Emmi Takkinen <emmi.takkinen@outlook.com>
Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

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

C4/Items.pm

@@ -1379,7 +1379,7 @@ sub _SearchItems_build_where_fragment {
             }
 
             if ( defined $ifnull ) {
-                $column = "IFNULL($column, ?)";
+                $column = "COALESCE($column, ?)";
             }
 
             if (ref $query eq 'ARRAY') {