BUG #8613: getting null when null is concatenated with string

The following bug has been logged on the website:

Bug reference: 8613
Logged by: rajasekhar5c1
Email address: rajasekhar5c1(at)gmail(dot)com
PostgreSQL version: 9.2.1
Operating system: linux
Description:

when i fire below query on one of our servers

select null || 'query' ,'|'

the result is null nothing is displayed

when i fire the same query on another server which has same version of
postgresql server

i am getting result as

query

postgres version on both servers are

1) EnterpriseDB 9.2.1.3 on i686-pc-linux-gnu, compiled by gcc (GCC) 4.1.2
20080704 (Red Hat 4.1.2-52), 32-bit 2) EnterpriseDB 9.2.1.3 on
x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.1.2 20080704 (Red Hat
4.1.2-52), 64-bit

why this different behavior?