NullPointerException exception when executing a g.E() request

After deleting and re-creating the edge label, connections with this label were interrupted, and when executing the `g.E()` request, as well as when trying to create a backup, a `NullPointerException` error occurs.
Is it possible to somehow remove the broken connections without recreating the graph?
The edge label was recreated to change multiplicity from `Multiplicity.ONE2MANY` to `Multiplicity.MULTI`.

backend - cassandra
versions - 0.6.1 and 0.5.2
graph - `org.janusgraph.core.ConfiguredGraphFactory`

migration script :
``` groovy
graph = ConfiguredGraphFactory.open("graph")
management = graph.openManagement()

management.getEdgeLabel("worked_in").remove()
management.commit()

management = graph.openManagement()
workedIn = management.makeEdgeLabel("worked_in").multiplicity(Multiplicity.MULTI).make()
employee = management.getVertexLabel("Employee")
expirience = management.getVertexLabel("PreviousExperience")

management.addConnection(workedIn, employee, expirience)
management.commit()
```

Start with the reported migration script using ConfiguredGraphFactory, edge-label removal and recreation, and the subsequent g.E() and backup operations. Reproduce the NullPointerException on Cassandra with the stated 0.6.1 or 0.5.2 versions, then determine whether the broken connections can be removed without recreating the graph.

Written by the indexing model from the issue text.