NPE while handling PORT_REMOVED event on ONU Deletion

Getting following NullPointerException in ONOS AAA app when a BBSIM ONU is disabled + deleted using voltctl command 

2020-02-12 09:42:36,385 | INFO | onos-of-worker-0 | DeviceManager | 130 - org.onosproject.onos-core-net - 1.13.9 | Device of:00000a0a0a0a0a00 port 19 status changed
2020-02-12 09:42:36,385 | WARN | spatch-topology0 | ListenerRegistry | 128 - org.onosproject.onos-api - 1.13.9 | Exception encountered while processing event DeviceEvent{time=2020-02-12T09:42:36.384Z, type=PORT_REMOVED, subject=DefaultDevice

{id=of:00000a0a0a0a0a00, type=SWITCH, manufacturer=VOLTHA Project, hwVersion=open_pon, swVersion=open_pon, serialNumber=BBSIM_OLT_0, driver=voltha}

, port=DefaultPort{element=of:00000a0a0a0a0a00, number=19, isEnabled=false, type=FIBER, portSpeed=0, annotations=

{adminState=disabled, portName=BBSM00000001-4, portMac=08:00:00:00:00:13}

}}
java.lang.NullPointerException
at org.opencord.aaa.impl.AaaSupplicantMachineStatsManager.getSupplicantStats(AaaSupplicantMachineStatsManager.java:66)[179:org.opencord.aaa-app:1.10.0]
at org.opencord.aaa.impl.AaaManager$InternalDeviceListener.event(AaaManager.java:969)[179:org.opencord.aaa-app:1.10.0]
at org.opencord.aaa.impl.AaaManager$InternalDeviceListener.event(AaaManager.java:953)[179:org.opencord.aaa-app:1.10.0]
at org.onosproject.event.ListenerRegistry.process(ListenerRegistry.java:66)[128:org.onosproject.onos-api:1.13.9]
at org.onosproject.event.impl.CoreEventDispatcher$DispatchLoop.process(CoreEventDispatcher.java:203)[130:org.onosproject.onos-core-net:1.13.9]
at org.onosproject.event.impl.CoreEventDispatcher$DispatchLoop.run(CoreEventDispatcher.java:185)[130:org.onosproject.onos-core-net:1.13.9]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)[:1.8.0_202]
at java.util.concurrent.FutureTask.run(FutureTask.java:266)[:1.8.0_202]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)[:1.8.0_202]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)[:1.8.0_202]
at java.lang.Thread.run(Thread.java:748)[:1.8.0_202]

 

This seems to happen for PORT_REMOVED event for each port of ONU for which there is no AAA session present in ONOS AAA app e.g. port 17, 18, 19 (and not port 16)

 

Steps to Reproduce:

• Start kind-voltha minimal setup with BBSIM and RADIUS
• Create and Enable OLT using voltctl device commands
• Let ONU be discovered and become ACTIVE.
• Disable and Delete ONU using voltctl device commands