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@gmail.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?