Added a missing argument to the set_error() method.
This omission was spotted by Edward d'Auvergne in a post at: https://mail.gna.org/public/relax-devel/2008-04/msg00053.html (# Message-id: <7f080ed10804111525p48f7bc6aq10189644ae5d736b@...>)
Authored by: semor 2008-04-12
Parent: [r5594]
Child: [r5596]
