BUG #12242: No error - if there is no comma seperator

The following bug has been logged on the website:

Bug reference:      12242
Logged by:          Onkar Gaonkar
Email address:      omkar1103@gmail.com
PostgreSQL version: 9.3.3
Operating system:   Windows
Description:

Below script does not throw error
=======================================
SELECT
claim_status,
claim_key
FROM tbl_claim
WHERE claim_key IN
(
'1140799265'
'2129945595'
)
=======================================


Throws Error
=======================================
SELECT
claim_status,
claim_key
FROM tbl_claim
WHERE claim_key IN
(
'1140799265' '2129945595'
)


ERROR:  syntax error at or near "'2129945595'"
LINE 7: '1140799265' '2129945595'
                     ^
********** Error **********
ERROR: syntax error at or near "'2129945595'"
SQL state: 42601
Character: 113
=======================================