BUG #15763: JSON nulls not handled properly

The following bug has been logged on the website:

Bug reference:      15763
Logged by:          Jacob Crell
Email address:      jacobcrell@gmail.com
PostgreSQL version: 9.6.8
Operating system:   AWS RDS
Description:

SELECT '{"test":null}'::json->>'test' will return a null
SELECT '{"test":null}'::json->'test' will return a string 'null'
The 2nd option seems like it should also return a null.