NullPointerException on the initialization of alto provider

I observed that NullPointer Exception occurred on the initialization of alto provider.

This issue occurred in the CSIT for Lithium release.
https://jenkins.opendaylight.org/releng/view/vtn/job/vtn-csit-1node-cds-manager-all-stable-lithium/147/artifact/karaf.log

This caused that other MD-SAL applications (e.g. VTN Manager) failed to initialize.

Error log message
=================

2015-06-16 20:01:06,235 | ERROR | config-pusher | ConfigTransactionControllerImpl | 126 - org.opendaylight.controller.config-manager - 0.3.0.SNAPSHOT | Commit failed on ModuleIdentifier

{factoryName='alto-host-tracker-impl', instanceName='alto-host-tracker-impl'}

in transaction TransactionIdentifier

{name='ConfigTransaction-200-202'}

java.lang.NullPointerException
at org.opendaylight.alto.altohosttracker.plugin.internal.AltoHostTrackerImpl.registerAsDataChangeListener(AltoHostTrackerImpl.java:690)
at org.opendaylight.yang.gen.v1.urn.opendaylight.alto.alto.host.tracker.impl.rev140528.AltoHostTrackerModule.createInstance(AltoHostTrackerModule.java:40)
at org.opendaylight.controller.config.spi.AbstractModule.getInstance(AbstractModule.java:73)