as described in JPA:

/**

• Execute a SELECT query that returns a single untyped result.
• @return the result
• @throws NoResultException if there is no result
• @throws NonUniqueResultException if more than one result
• @throws IllegalStateException if called for a Java
• Persistence query language UPDATE or DELETE statement
• @throws QueryTimeoutException if the query execution exceeds
• the query timeout value set and only the statement is
• rolled back
• @throws TransactionRequiredException if a lock mode other than
• <code>NONE</code> has been set and there is no transaction
• or the persistence context has not been joined to the transaction
• @throws PessimisticLockException if pessimistic locking
• fails and the transaction is rolled back
• @throws LockTimeoutException if pessimistic locking
• fails and only the statement is rolled back
• @throws PersistenceException if the query execution exceeds
• the query timeout value set and the transaction
• is rolled back
  */
  Object getSingleResult();

getSingleResult should throw NoResultException, but in Hibernate 5.2 it does not thrown, and returns null instead. my code is:
entityManager.createNamedQuery("some query")
.getSingleResult()