Critical bug: query result is wrong when Column is Null

[kangkaisen]

Describe the bug
The query result is wrong.

To Reproduce
Steps to reproduce the behavior:
1 create table

CREATE TABLE `test_wrong_result` (
  `a` int(11),
  `b` tinyint(4),
  `c` tinyint(4),
  `d` bigint(20)
) ENGINE=OLAP
DUPLICATE KEY(`a`, `b`, `c`,  `d`)
DISTRIBUTED BY HASH(`d`) BUCKETS 10;

2 load the data

3001	3	\N	1090050

3 query

SELECT c FROM test_wrong_result WHERE a = 3001 and b = 3 and d = 1090050;

Expected behavior
The query result should be NULL, not Empty set.