NullPointerException when unmarshalling after eviction thread has been cancelled

See the parent issue ISPN-697 , which contains more details and an application which can occasionally reproduce the NPE.

2010-10-11 15:55:27,305 ERROR [Scheduled-eviction-thread-0] (FileCacheStore.java:184) - Error while reading from file: /home/cching/dev/infinispan-hang/./store/Users/-202784536
java.lang.NullPointerException
at org.infinispan.marshall.jboss.ConstantObjectTable.readObject(ConstantObjectTable.java:253)
at org.jboss.marshalling.river.RiverUnmarshaller.doReadObject(RiverUnmarshaller.java:357)
at org.jboss.marshalling.river.RiverUnmarshaller.doReadObject(RiverUnmarshaller.java:207)
at org.jboss.marshalling.AbstractUnmarshaller.readObject(AbstractUnmarshaller.java:85)
at org.infinispan.marshall.jboss.GenericJBossMarshaller.objectFromObjectStream(GenericJBossMarshaller.java:162)
at org.infinispan.marshall.VersionAwareMarshaller.objectFromObjectStream(VersionAwareMarshaller.java:179)
at org.infinispan.loaders.file.FileCacheStore.objectFromInputStreamInReentrantMode(FileCacheStore.java:262)
at org.infinispan.loaders.file.FileCacheStore.loadBucket(FileCacheStore.java:181)
at org.infinispan.loaders.file.FileCacheStore.purgeInternal(FileCacheStore.java:161)
at org.infinispan.loaders.AbstractCacheStore$2.run(AbstractCacheStore.java:84)
at org.infinispan.util.concurrent.WithinThreadExecutor.execute(WithinThreadExecutor.java:47)
at org.infinispan.loaders.AbstractCacheStore.purgeExpired(AbstractCacheStore.java:81)
at org.infinispan.eviction.EvictionManagerImpl.processEviction(EvictionManagerImpl.java:115)
at org.infinispan.eviction.EvictionManagerImpl$ScheduledTask.run(EvictionManagerImpl.java:136)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:98)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.runPeriodic(ScheduledThreadPoolExecutor.java:181)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:205)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)