Add action Desaturate violates not-null constraint

Trying to add an action "Add Desaturate" to a preset, results is the following warnings:

* warning: pg_query(): Query failed: ERROR: null value in column "data" violates not-null constraint in /srv/www/htdocs/gpsweather/includes/database.pgsql.inc on line 139.
* user warning: query: INSERT INTO imagecache_action (presetid, weight, module, action) VALUES (1, 0, 'imagecache', 'imagecache_desaturate') in /srv/www/htdocs/gpsweather/includes/common.inc on line 3436.

and the action is not added to the preset.

The action "desaturate" takes no parameters except for the weight, so apparently the data field should in fact be NULL.

Disabling the "NOT NULL" constraint on the database, removes the problem and inserts the row with the value of the data field set to NULL. In this case the actual desaturation of the image is performed correctly.