The following bug has been logged online:

Bug reference: 1568
Logged by: helman
Email address: 123 (AT) 123 (DOT) com
PostgreSQL version: 8.0
Operating system: linux
Description: concat
Details:

concat no accept null

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helman wrote:
Concatting a NULL returns a NULL. You might want to use COALESCE() to
return '' for NULL in the concat.

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