Exceptions are thrown while processing filtration on links on Inventory model.

Exceptions:
java.lang.IllegalStateException: Processing new request for topology change failed.
at org.opendaylight.topoprocessing.impl.request.TopologyRequestHandler.processNewRequest(TopologyRequestHandler.java:199)[236:org.opendaylight.topoprocessing.impl:0.1.0.SNAPSHOT]
...
Caused by: java.lang.NullPointerException
at org.opendaylight.topoprocessing.impl.translator.PathTranslator.translate(PathTranslator.java:71)[236:org.opendaylight.topoprocessing.impl:0.1.0.SNAPSHOT]

These exceptions are thrown when input model of underlay topology and output model of overlay topology are set to Inventory model while translating target-field path.