BUG #14439: Trigger function fails with internal error after upgrade to 9.6

The following bug has been logged on the website:

Bug reference: 14439
Logged by: Maxim Valyanskiy
Email address: max(dot)valjanski(at)gmail(dot)com
PostgreSQL version: 9.6.1
Operating system: CentOS 6.8
Description:

Trigger function stopped working after upgrade from 9.5 to 9.6. Upgrade was
performed via pg_upgrade.

This is that error output:

# update ab_group set name='Domain Controllerz' where id=466;
ERROR: table row type and query-specified row type do not match
ПОДРОБНОСТИ: Query provides a value for a dropped column at ordinal
position 6.
КОНТЕКСТ: SQL statement "UPDATE ab_group SET name_gin =
to_tsvector('simple', NEW.name) WHERE id = NEW.id AND NEW.name <>
OLD.name"
PL/pgSQL function update_group_name_gin() line 4 at SQL statement

I tried to recreate function, made VACUUM FULL and CLUSTER for that table
and it did not fix the problem.

Here is source code for that function:

CREATE OR REPLACE FUNCTION public.update_group_name_gin()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
BEGIN
IF (TG_OP = 'UPDATE') THEN
UPDATE ab_group SET name_gin = to_tsvector('simple',
NEW.name) WHERE id = NEW.id AND NEW.name <> OLD.name;
RETURN NEW;
ELSIF (TG_OP = 'INSERT') THEN
UPDATE ab_group SET name_gin = to_tsvector('simple',
NEW.name) WHERE id = NEW.id;
END IF;
RETURN NULL;
END;
$function$