SELECT DISTINCT is not picking empty strings

SELECT DISTINCT is not picking empty strings.

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 distinct b from t1;
----------

b
----------

NULL

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

Columnstore> select distinct b from t1;
----------

b
----------

NULL
hello
HELLO
HELLO MY
NewBlob
----------
5 rows in set (0.008 sec)