When the queue contains a BatchTask, and you shutdown Hudson, it will be
persisted to queue.xml. On restart, the BatchTask in the queue will NOT have
links to owner or parent. On rendering the queue, this will cause a NPE in
BatchTask.getFullDisplayName(), making the home page unavailable.

SEVERE: Failed to initialize Hudson
java.lang.NullPointerException
at
hudson.plugins.batch_task.BatchTask.getFullDisplayName(BatchTask.java:67)
at hudson.model.Queue.add(Queue.java:298)
at hudson.model.Queue.load(Queue.java:182)
at hudson.model.Hudson.<init>(Hudson.java:479)
at hudson.WebAppMain$2.run(WebAppMain.java:160)
Exception in thread "hudson initialization thread"
java.lang.NullPointerException