exception in group statistics when use Nicira extension action

Add the following group to ovs, the exception is observed.

group_id=1,type=all,bucket=weight:0,actions=load:0xc0a81465->NXM_NX_TUN_IPV4_DST[],output:1,bucket=weight:0,actions=load:0xc0a81466->NXM_NX_TUN_IPV4_DST[],output:1

exception:
2016-01-08 18:23:51,955 | WARN | ds-oper-thread-0 | StatisticsManagerImpl | 261 - org.opendaylight.openflowplugin.applications.statistics-manager - 0.2.0.SNAPSHOT | Unhandled exception during processing statistics. Restarting transaction chain.
org.opendaylight.yangtools.binding.data.codec.impl.IncorrectNestingException: Supplied class interface org.opendaylight.yang.gen.v1.urn.opendaylight.openflowplugin.extension.nicira.action.rev140714.group.desc.stats.updated.group.desc.stats.buckets.bucket.action.action.NxActionRegLoadNotifGroupDescStatsUpdatedCase is not valid case
at org.opendaylight.yangtools.binding.data.codec.impl.IncorrectNestingException.create(IncorrectNestingException.java:28)
at org.opendaylight.yangtools.binding.data.codec.impl.DataContainerCodecContext.childNonNull(DataContainerCodecContext.java:180)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.impl.ChoiceNodeCodecContext.streamChild(ChoiceNodeCodecContext.java:110)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.impl.BindingToNormalizedStreamWriter.enter(BindingToNormalizedStreamWriter.java:67)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.impl.BindingToNormalizedStreamWriter.startCase(BindingToNormalizedStreamWriter.java:134)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yang.gen.v1.urn.opendaylight.openflowplugin.extension.nicira.action.rev140714.group.desc.stats.updated.group.desc.stats.buckets.bucket.action.action.NxActionRegLoadNotifGroupDescStatsUpdatedCase$StreamWriter.serialize(DataObjectSerializerPrototype.java)[269:org.opendaylight.openflowplugin.extension-nicira:0.2.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.impl.BindingNormalizedNodeCodecRegistry$DataObjectSerializerProxy.serialize(BindingNormalizedNodeCodecRegistry.java:295)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.util.ChoiceDispatchSerializer.serialize(ChoiceDispatchSerializer.java:47)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yang.gen.v1.urn.opendaylight.action.types.rev131112.action.list.Action$StreamWriter.serialize(DataObjectSerializerPrototype.java)[248:org.opendaylight.openflowplugin.model.flow-base:0.2.0.SNAPSHOT]
at org.opendaylight.yang.gen.v1.urn.opendaylight.group.types.rev131018.group.buckets.Bucket$StreamWriter.serialize(DataObjectSerializerPrototype.java)[248:org.opendaylight.openflowplugin.model.flow-base:0.2.0.SNAPSHOT]
at org.opendaylight.yang.gen.v1.urn.opendaylight.group.types.rev131018.group.Buckets$StreamWriter.serialize(DataObjectSerializerPrototype.java)[248:org.opendaylight.openflowplugin.model.flow-base:0.2.0.SNAPSHOT]
at org.opendaylight.yang.gen.v1.urn.opendaylight.group.statistics.rev131111.group.desc.GroupDesc$StreamWriter.serialize(DataObjectSerializerPrototype.java)[249:org.opendaylight.openflowplugin.model.flow-statistics:0.2.0.SNAPSHOT]
at org.opendaylight.yang.gen.v1.urn.opendaylight.group.statistics.rev131111.NodeGroupDescStats$StreamWriter.serialize(DataObjectSerializerPrototype.java)[249:org.opendaylight.openflowplugin.model.flow-statistics:0.2.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.impl.BindingNormalizedNodeCodecRegistry$DataObjectSerializerProxy.serialize(BindingNormalizedNodeCodecRegistry.java:295)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.util.AugmentableDispatchSerializer.emitAugmentation(AugmentableDispatchSerializer.java:79)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.util.AugmentableDispatchSerializer.serialize(AugmentableDispatchSerializer.java:51)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yang.gen.v1.urn.opendaylight.group.types.rev131018.groups.Group$StreamWriter.serialize(DataObjectSerializerPrototype.java)[248:org.opendaylight.openflowplugin.model.flow-base:0.2.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.impl.BindingNormalizedNodeCodecRegistry$DataObjectSerializerProxy.serialize(BindingNormalizedNodeCodecRegistry.java:295)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.yangtools.binding.data.codec.impl.BindingNormalizedNodeCodecRegistry.toNormalizedNode(BindingNormalizedNodeCodecRegistry.java:106)[93:org.opendaylight.mdsal.binding-dom-codec:0.8.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.binding.impl.BindingToNormalizedNodeCodec.toNormalizedNode(BindingToNormalizedNodeCodec.java:133)[143:org.opendaylight.controller.sal-binding-broker-impl:1.3.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.binding.impl.AbstractWriteTransaction.put(AbstractWriteTransaction.java:39)[143:org.opendaylight.controller.sal-binding-broker-impl:1.3.0.SNAPSHOT]
at org.opendaylight.controller.md.sal.binding.impl.BindingDOMWriteTransactionAdapter.put(BindingDOMWriteTransactionAdapter.java:40)[143:org.opendaylight.controller.sal-binding-broker-impl:1.3.0.SNAPSHOT]
at org.opendaylight.openflowplugin.applications.statistics.manager.impl.StatListenCommitGroup.statGroupDescCommit(StatListenCommitGroup.java:332)[261:org.opendaylight.openflowplugin.applications.statistics-manager:0.2.0.SNAPSHOT]
at org.opendaylight.openflowplugin.applications.statistics.manager.impl.StatListenCommitGroup.access$100(StatListenCommitGroup.java:73)[261:org.opendaylight.openflowplugin.applications.statistics-manager:0.2.0.SNAPSHOT]
at org.opendaylight.openflowplugin.applications.statistics.manager.impl.StatListenCommitGroup$1.applyOperation(StatListenCommitGroup.java:138)[261:org.opendaylight.openflowplugin.applications.statistics-manager:0.2.0.SNAPSHOT]
at org.opendaylight.openflowplugin.applications.statistics.manager.impl.StatisticsManagerImpl.run(StatisticsManagerImpl.java:186)[261:org.opendaylight.openflowplugin.applications.statistics-manager:0.2.0.SNAPSHOT]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)[:1.8.0_45-internal]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)[:1.8.0_45-internal]
at java.lang.Thread.run(Thread.java:745)[:1.8.0_45-internal]

The reason may be because only augment the notification, no augment the operational datastore.