Insert default value failed when column is nullable and do not set default value explicitly

[zhangy5]

Describe the bug
Create table like

CREATE TABLE d (
k1 int(11) NULL COMMENT "",
k2 int(11) NULL COMMENT ""
) ENGINE=OLAP
AGGREGATE KEY(k1, k2)
DISTRIBUTED BY HASH(k1) BUCKETS 5
PROPERTIES (
"storage_type" = "COLUMN"
);

When I insert data failed.

mysql> insert into d (k1) values (1);
ERROR 5002 (HY000): 'k2' must be explicitly mentioned in column permutation

It is expected that this insert will be succeeded, and the value of k2 is null.

[EmmyMiao87]

#1556