Release rollback hangs when the release failed at the scm-check-modifications phase

To reproduce
1. introduce a local change to the working copy
2. attempt to release the project
3. release fails at the scm-check-modifications phase
4. click Rollback
5. Confirm rollback

Result:
Web UI hangs at "Opening page ... releaseRollback.action"
Stack trace in log
...
INFO | jvm 1 | 2008/09/18 14:59:24 | 2008-09-18 14:59:24,178 [pool-5-thread-1] ERROR taskQueueExecutor#rollback-release - Error executing task
INFO | jvm 1 | 2008/09/18 14:59:24 | org.codehaus.plexus.taskqueue.execution.TaskExecutionException: Failed to rollback release
...
INFO | jvm 1 | 2008/09/18 14:59:24 | Caused by: org.apache.maven.shared.release.ReleaseExecutionException: Cannot restore from a missing backup POM: /path/to/continuum/working-directory/2/pom.xml.releaseBackup

It should be able to roll back from a failure at any point, or the rollback button should be disabled if it's not relevant.