Version: 5.0.0

If the ORB is created with system property -Dorg.omg.CORBA.SkipGmbalInit=true (see #204), a NullPointerException is thrown when shutting down, because POAFactory#removePoaManager expects a non-null ManagedObjectManager in field mom. But that field is null, because it's initialized from com.sun.corba.ee.spi.orb.ORB#mom, which is null with above system property.

java.lang.NullPointerException: Cannot invoke "org.glassfish.gmbal.ManagedObjectManager.unregister(Object)" because "this.mom" is null
	at com.sun.corba.ee.impl.oa.poa.POAFactory.removePoaManager(POAFactory.java:246)
	at com.sun.corba.ee.impl.oa.poa.POAManagerImpl$POAManagerDeactivator.run(POAManagerImpl.java:556)
	at com.sun.corba.ee.impl.oa.poa.POAManagerImpl.deactivate(POAManagerImpl.java:492)
	at com.sun.corba.ee.impl.oa.poa.POAFactory.shutdown(POAFactory.java:236)
	at com.sun.corba.ee.impl.orb.ORBImpl.shutdownServants(ORBImpl.java:1395)
	at com.sun.corba.ee.impl.orb.ORBImpl.shutdown(ORBImpl.java:1355)
	at com.sun.corba.ee.impl.orb.ORBImpl.destroy(ORBImpl.java:1448)

Let me add some context, why I ended up trying to use that system property:

• With version 4.2.2, we excluded the gmbal dependency and replaced it with gmbal-api-only because the former requires a huge additional amount of heap memory (65MB in our case, compare [PERF] gmbal objects consuming large part of heap #5). Replacing the dependency worked fine though.
• Version 5.0.0 does not have a dependency on gmbal anymore, but on gmbal-api-only only. But we have to set org.omg.CORBA.SkipGmbalInit=true now because otherwise org.glassfish.gmbal.ManagedObjectManagerFactory throws an IllegalStateException in its class initializer if the implementation from gmbal is not available (since Fixed cyclic dependency between api and impl forbidden by JPMS orb-gmbal#56).