Currently, IMObjectBean, EntityBean and ActBean all ignore non-null references that fail to resolve to a corresponding IMObject.
This is typically an error, as it either means that the corresponding object:
1. has not yet been saved
2. the has been deleted but is still referenced.
The latter should be disallowed by the schema, but our use of hibernate means that the appropriate foreign key constraints are not created.
In both cases, detecting the error is preferred to ignoring it completely.