HttpNeo4jDialect runs into NPE in getAssociation() (line 320) during a commit of a transaction after persisting of an object graph with bidirectional and polymorphic associations.
Corresponding test case can be found in https://github.com/dadrus/jpa-unit/blob/13-neo4j-support/integration-test/base/src/main/java/eu/drus/jpa/unit/test/AbstractCleanupTest.java (test1(), line 37). It can be started using https://github.com/dadrus/jpa-unit/blob/13-neo4j-support/integration-test/jpa-neo4j-hibernate-ogm-test/src/test/java/eu/drus/jpa/unit/test/CleanupTest.java (@Ignore on a class level needs to be removed). Prerequisite to run the test is a running Neo4j instance (see https://github.com/dadrus/jpa-unit/blob/13-neo4j-support/integration-test/jpa-neo4j-hibernate-ogm-test/src/test/resources/META-INF/persistence.xml for further settings).
It is actually the same behavior as encountered with BoltNeo4jDialect (see OGM-1303). Only the following settings in the persistence.xml differ from the referenced issue: