SELECT GROUP BY is not picking not-NULL values

SELECT GROUP BY is not picking not-NULL values

Repro
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create table t1 (t text,c char(10),b blob) engine = columnstore;
insert into t1 values (NULL,NULL,NULL);
insert into t1 values ("","","");
insert into t1 values ("hello","hello","hello");
insert into t1 values ("HELLO","HELLO","HELLO");
insert into t1 values ("HELLO MY","HELLO MY","HELLO MY");
insert into t1 values ("a","a","a");
insert into t1 values (1,1,1);
insert into t1 values (NULL,NULL,NULL);
update t1 set c="",b=null where c="1";
update t1 set b="NewBlob" where c="a";
update t1 set t="newhello", c="newhello" where b="hello";

InnoDB> select b from cst1 group by b;
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b
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NULL

HELLO
HELLO MY
NewBlob
hello
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6 rows in set (0.001 sec)

Columnstore> select b from cst1 group by b;
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b
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NULL
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1 row in set (0.047 sec)