How to resolve [A collection with cascade=“all-delete-orphan” was no longer referenced by the owning entity instance]

1. http://codippa.com/how-to-resolve-a-collection-with-cascadeall-delete-orphan-was-no-longer-referenced-by-the-owning-entity-instance/
2. http://cristian.sulea.net/blog.php?p=2014-06-28-hibernate-exception-a-collection-with-cascade-all-delete-orphan-was-no-longer-referenced-by-the-owning-entity-instance