May be a jsonb type bug

Hi all:

When i exec function jsonb_array_length(jsonb)，The database throw a
error: |cannot get array length of a scalar
That's because have a 'null' value in the jsonb type column|

|So i have a test and think null is a bug for jsonb:
|

mydb=# \d test
                                       Table "public.test"
  Column  |            Type             | Collation | Nullable
|             Default
----------+-----------------------------+-----------+----------+----------------------------------
 id       | integer                     |           | not null |
nextval('test_id_seq'::regclass)
 info     | text                        |           |          |
 crt_time | timestamp without time zone |           |          |
 col_n    | jsonb                       |           |          |
Indexes:
    "test_pkey" PRIMARY KEY, btree (id)

mydb=# update test set col_n='test' where id=1;
ERROR:  invalid input syntax for type json
LINE 1: update test set col_n='test' where id=1;
                              ^
DETAIL:  Token "test" is invalid.
CONTEXT:  JSON data, line 1: test

mydb=# update test set col_n='null' where id=1;
UPDATE 1
mydb=#
mydb=#
mydb=# select * from test where id=1;
 id | info |          crt_time          | col_n
----+------+----------------------------+-------
  1 | test | 2017-12-13 15:14:16.347681 | null
(1 row)

--
*PostgreSQL DBA yunlong.gao *

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