NullPointerException at org.opendaylight.genius.interfacemanager.rpcservice.InterfaceManagerRpcService.getDpnInterfaceList

I regularly hit the following NPE when "playing around" - I think it's when I have a running ODL & devstack, and stop the Karaf and restart it, something doesn't quite go the way it expects:

2017-03-16 18:16:43,008 | WARN | eChangeHandler-0 | TunnelInterfaceStateListener | 365 - org.opendaylight.netvirt.vpnmanager-impl - 0.4.0.SNAPSHOT | Exception when querying for GetDpnInterfaceList for dpnid 73240449055560
java.lang.NullPointerException
at org.opendaylight.genius.interfacemanager.rpcservice.InterfaceManagerRpcService.getDpnInterfaceList(InterfaceManagerRpcService.java:491)[357:org.opendaylight.genius.interfacemanager-impl:0.2.0.SNAPSHOT]
at org.opendaylight.yangtools.yang.binding.util.RpcMethodInvokerWithInput.invokeOn(RpcMethodInvokerWithInput.java:31)[74:org.opendaylight.mdsal.yang-binding:0.10.0.SNAPSHOT]
at org.opendaylight.yangtools.yang.binding.util.AbstractMappedRpcInvoker.invokeRpc(AbstractMappedRpcInvoker.java:52)[74:org.opendaylight.mdsal.yang-binding:0.10.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.binding.impl.BindingDOMRpcImplementationAdapter.invoke(BindingDOMRpcImplementationAdapter.java:85)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.binding.impl.BindingDOMRpcImplementationAdapter.invokeRpc(BindingDOMRpcImplementationAdapter.java:72)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.dom.broker.impl.GlobalDOMRpcRoutingTableEntry.invokeRpc(GlobalDOMRpcRoutingTableEntry.java:39)[171:org.opendaylight.controller.sal-broker-impl:1.5.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.dom.broker.impl.DOMRpcRoutingTable.invokeRpc(DOMRpcRoutingTable.java:177)[171:org.opendaylight.controller.sal-broker-impl:1.5.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.dom.broker.impl.DOMRpcRouter.invokeRpc(DOMRpcRouter.java:102)[171:org.opendaylight.controller.sal-broker-impl:1.5.0.SNAPSHOT]
at Proxy72e63eb6_e1b9_4b09_a6fc_36aa34e5f4cd.invokeRpc(Unknown Source)[:]
at Proxy1ab30bfb_17bc_4868_aac8_f3c06f8608a3.invokeRpc(Unknown Source)[:]
at org.opendaylight.controller.md.sal.binding.impl.RpcServiceAdapter.invoke0(RpcServiceAdapter.java:65)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.binding.impl.RpcServiceAdapter.access$000(RpcServiceAdapter.java:43)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.binding.impl.RpcServiceAdapter$RpcInvocationStrategy.invoke(RpcServiceAdapter.java:159)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.binding.impl.RpcServiceAdapter.invoke(RpcServiceAdapter.java:96)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.0.SNAPSHOT]
at com.sun.proxy.$Proxy135.getDpnInterfaceList(Unknown Source)[329:org.opendaylight.genius.interfacemanager-api:0.2.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.TunnelInterfaceStateListener.handleTunnelEventForDPN(TunnelInterfaceStateListener.java:201)[365:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.TunnelInterfaceStateListener.add(TunnelInterfaceStateListener.java:136)[365:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.TunnelInterfaceStateListener.add(TunnelInterfaceStateListener.java:50)[365:org.opendaylight.netvirt.vpnmanager-impl:0.4.0.SNAPSHOT]
at org.opendaylight.genius.datastoreutils.AsyncDataTreeChangeListenerBase$DataTreeChangeHandler.run(AsyncDataTreeChangeListenerBase.java:153)[326: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]