Anonymous users are unable to add products to cart

When an anonymous user tries to add a product to his shopping cart, a PDOException occurs. Here is the actual error message:

PDOException: SQLSTATE[22P02]: Invalid text representation: 7 ERROR: invalid input syntax for integer: "5a1517558180de423e23eb37d570a38f" LINE 4: WHERE (base.uid IN ('5a1517558180de423e23eb37d570a38f')) ^: SELECT base.uid AS uid, base.name AS name, base.pass AS pass, base.mail AS mail, base.theme AS theme, base.signature AS signature, base.signature_format AS signature_format, base.created AS created, base.access AS access, base.login AS login, base.status AS status, base.timezone AS timezone, base.language AS language, base.picture AS picture, base.init AS init, base.data AS data FROM {users} base WHERE (base.uid IN (:db_condition_placeholder_0)) ; Array ( [:db_condition_placeholder_0] => 5a1517558180de423e23eb37d570a38f ) in DrupalDefaultEntityController->load() (line 196 of /var/websites/zzzzzzzzzzzzzz/htdocs/includes/entity.inc).

PostgreSQL cannot cast the session hash string to an integer and generates a PDOException. I am attaching a patch which fixes the issue. It is not tested thoroughly but seems to work.