Crash in my_decimal2decimal in a ORDER BY query

set @@time_zone='+00:00';

drop table if exists t1;

create table t1 (a datetime(4) not null);

insert into t1 values ('2001-01-01 00:00:00'),('2000-00-00 00:00:00');

select unix_timestamp(a) from t1 order by 1;