BUG #13494: Postgresql database displays first column data on merging of two columns in the Select statement

The following bug has been logged on the website:

Bug reference:      13494
Logged by:          Atul Srivastava
Email address:      atulcs178@gmail.com
PostgreSQL version: 9.1.9
Operating system:   Windows 7
Description:

PostgreSQL database displays data of the first column,under second column
name, When we merge two columns in the Select statement. However it should
throw error if we don't put any comma (,) in between both columns.

Note : We are getting error message like ("syntax error"). if we are trying
to merge three columns. However it is not throwing any error if we merged
two columns (it's just showing data of the first column,under second column
name)