Concurreny in org.apache.openjpa.persistence.EntityManagerImpl.getProperties leads to NullPointer and ConcurrentModificationException

A call of EntityManager.getProperties() can lead to NullPointer and ConcurrentModificationException. Issue occurs right after start up of the overlying JEE application if multiple EntityManager instance are created at same time.

Please find the issued stack trace below:

Caused by: java.lang.NullPointerException
at java.lang.String.compareTo(String.java:482)
at java.lang.String.compareTo(String.java:31)
at java.util.TreeMap.cmp(TreeMap.java:4514)
at java.util.TreeMap.putImpl(TreeMap.java:4556)
at java.util.TreeMap.put(TreeMap.java:4536)
at java.util.TreeSet.add(TreeSet.java:122)
at
org.apache.openjpa.lib.conf.ConfigurationImpl.getPropertyKeys(ConfigurationImpl.java:708)
at
org.apache.openjpa.kernel.BrokerImpl.getSupportedProperties(BrokerImpl.java:729)
at
org.apache.openjpa.kernel.DelegatingBroker.getSupportedProperties(DelegatingBroker.java:223)
at
org.apache.openjpa.persistence.EntityManagerImpl.getProperties(EntityManagerImpl.java:1624)
... 33 more