Permissions of implicit domains are left after the table is dropped

[asfernandes]

create table t1 (n1 integer);
commit;

select * from rdb$fields where rdb$field_name = 'RDB$1';
-- 1 record

select * from rdb$user_privileges where rdb$relation_name = 'RDB$1';
-- 1 record

drop table t1;
commit;

select * from rdb$fields where rdb$field_name = 'RDB$1';
-- 0 record

select * from rdb$user_privileges where rdb$relation_name = 'RDB$1';
-- 1 record