AtomicEvents crash

[colin-scott]

Another crash. This one came up after many delta debugging splits, so I'm guessing it's an issue with how we split atomic events.

Exception in thread "main" java.lang.RuntimeException: UnPartition without preceding Partition
        at akka.dispatch.verification.UnmodifiedEventDag$$anonfun$get_atomic_events$1.apply(Util.scala:217)
        at akka.dispatch.verification.UnmodifiedEventDag$$anonfun$get_atomic_events$1.apply(Util.scala:189)
        at scala.collection.immutable.List.foreach(List.scala:381)
        at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)
        at scala.collection.mutable.ListBuffer.foreach(ListBuffer.scala:45)
        at akka.dispatch.verification.UnmodifiedEventDag.get_atomic_events(Util.scala:189)
        at akka.dispatch.verification.EventDagView.get_atomic_events(Util.scala:266)
        at akka.dispatch.verification.DDMin.ddmin2(DeltaDebugging.scala:44)
        at akka.dispatch.verification.DDMin.ddmin2(DeltaDebugging.scala:78)
        at akka.dispatch.verification.DDMin.ddmin2(DeltaDebugging.scala:80)
        at akka.dispatch.verification.DDMin.ddmin2(DeltaDebugging.scala:80)
        at akka.dispatch.verification.DDMin.ddmin2(DeltaDebugging.scala:80)
        at akka.dispatch.verification.DDMin.ddmin2(DeltaDebugging.scala:80)
        at akka.dispatch.verification.DDMin.ddmin2(DeltaDebugging.scala:80)
        at akka.dispatch.verification.DDMin.ddmin2(DeltaDebugging.scala:78)
        at akka.dispatch.verification.DDMin.minimize(DeltaDebugging.scala:32)
        at akka.dispatch.verification.RunnerUtils$.randomDDMin(RunnerUtils.scala:72)
        at Main$.delayedEndpoint$Main$1(Runner.scala:146)
        at Main$delayedInit$body.apply(Runner.scala:89)
        at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
        at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
        at scala.App$$anonfun$main$1.apply(App.scala:76)
        at scala.App$$anonfun$main$1.apply(App.scala:76)
        at scala.collection.immutable.List.foreach(List.scala:381)
        at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)
        at scala.App$class.main(App.scala:76)
        at Main$.main(Runner.scala:89)
        at Main.main(Runner.scala)