This issue is caused by the performance improvement HHH-11032 Closed done on 5.4.4 (and backported on 5.3.11).

the symptom is a NPE when flushing a persisted entity containing a ElementCollection with null as one of the elements in the list.

a test case will be added as soon as this issue will get an id.

The NPE is also thrown when an automatic flush is triggered (when for example we call getResultList() on a native query).

upgrading to the latest 5.4.6 doesn't fix the issue not downgrading to 5.3.12 but downgrade to 5.4.3 fix the issue...
reverting