It seems that in 1.3.5 or earlier, the Space ID of a Space was not populated. Thus, in later versions, when the Space of a SpaceDescription is referenced, null is returned and problems may occur. (See CONF-4672.) This can be fixed by writing an upgrade task to match the Space Description in the Spaces table with the record in the Content table and set the Space ID.

NOTE: This only seems to occur when updating an instance from 1.3.5 -> 2.0 by pointing the instance to the old database. Doing a backup and restore seems to fix the null space ID.