Seen in https://logs.opendaylight.org/releng/jenkins092/netvirt-csit-1node-openstack-newton-nodl-v2-upstream-stateful-carbon/597/archives/odl1_karaf.log.gz

2017-05-21 04:35:54,289 | WARN | eChangeHandler-0 | VpnManagerImpl | 332 - org.opendaylight.netvirt.vpnmanager-impl - 0.4.0.SNAPSHOT | Failed to handle router GW flow in GW-MAC table. MAC address is missing for router-id 94e1024a-34ae-4cde-9960-3858159804c7
2017-05-21 04:35:54,289 | INFO | eChangeHandler-0 | VpnManagerImpl | 332 - org.opendaylight.netvirt.vpnmanager-impl - 0.4.0.SNAPSHOT | Installing ARP responder flows for 94e1024a-34ae-4cde-9960-3858159804c7 fixed-ips [10.10.10.12] on switch 207212111248512
2017-05-21 04:35:54,290 | INFO | eChangeHandler-0 | IdManager | 318 - org.opendaylight.genius.idmanager-impl - 0.2.0.SNAPSHOT | createIdPool called with input CreateIdPoolInput [_high=65535, _low=49152, _poolName=10.10.10.12, augmentation=[]]
2017-05-21 04:35:54,291 | INFO | eChangeHandler-0 | LockListener | 317 - org.opendaylight.genius.lockmanager-impl - 0.2.0.SNAPSHOT | Received add for lock 10.10.10.12 : Lock{getLockName=10.10.10.12, getLockOwner=AsyncDataTreeChangeListenerBase-DataTreeChangeHandler-0, augmentations={}}
2017-05-21 04:35:54,290 | ERROR | eChangeHandler-0 | AsyncDataTreeChangeListenerBase | 291 - org.opendaylight.genius.mdsalutil-api - 0.2.0.SNAPSHOT | Thread terminated due to uncaught exception: AsyncDataTreeChangeListenerBase-DataTreeChangeHandler-0
java.lang.NullPointerException: Supplied value may not be null
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:226)[38:com.google.guava:18.0.0]
at org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.types.rev130715.MacAddress.<init>(MacAddress.java:51)[54:org.opendaylight.mdsal.model.ietf-yang-types-20130715:2013.7.15.10-SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.arp.responder.ArpResponderUtil.getActions(ArpResponderUtil.java:205)[332:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.arp.responder.ArpResponderUtil.getExtInterfaceInstructions(ArpResponderUtil.java:234)[332:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.VpnManagerImpl.installArpResponderFlowsToExternalNetworkIp(VpnManagerImpl.java:287)[332:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.VpnManagerImpl.setupArpResponderFlowsToExternalNetworkIps(VpnManagerImpl.java:255)[332:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.VpnManagerImpl.setupArpResponderFlowsToExternalNetworkIps(VpnManagerImpl.java:230)[332:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at Proxy5edcabd8_d214_4506_a1bf_84e7e6bd0bd8.setupArpResponderFlowsToExternalNetworkIps(Unknown Source)[:]
at Proxy5edcabd8_d214_4506_a1bf_84e7e6bd0bd8.setupArpResponderFlowsToExternalNetworkIps(Unknown Source)[:]
at org.opendaylight.netvirt.vpnmanager.CentralizedSwitchChangeListener.setupRouterGwFlows(CentralizedSwitchChangeListener.java:113)[332:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.CentralizedSwitchChangeListener.add(CentralizedSwitchChangeListener.java:85)[332:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.CentralizedSwitchChangeListener.add(CentralizedSwitchChangeListener.java:38)[332:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.genius.datastoreutils.AsyncDataTreeChangeListenerBase$DataTreeChangeHandler.run(AsyncDataTreeChangeListenerBase.java:156)[291:org.opendaylight.genius.mdsalutil-api:0.2.0.SNAPSHOT]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)[:1.8.0_121]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)[:1.8.0_121]
at java.lang.Thread.run(Thread.java:745)[:1.8.0_121]