When using an audited entity collection of an embeddable:
This causes a NullPointerException to occur when fetching a revision of the Parent entity when the embeddable Item contains a non-null reference to Type, which is not audited. This is only an issue when the embeddable class holds a reference to a non-audited entity.
Based on porting your test case, it looks like the NullPointerException is thrown from:
Does that seem right based on your observation ?
Yes, exceptition thrown out from org.hibernate.envers.exception.AuditException: java.lang.NullPointerException
Fixed in 5.1 branch as well.