Spurious NullPointerException when restoring document from recycle bin

[michitux]

When restoring a document from the recycle bin, I got a NullPointerException in TaskMacroUpdateEventListener. The document did not contain any task and was imported from Confluence. I haven't tried reproducing in these specific conditions but I definitely couldn't reproduce in a more standard situation. Still, I think the stack trace has enough information where the null value occurred to allow adding some bulletproofing:

Failed to send event [org.xwiki.bridge.event.DocumentCreatingEvent@ea4b3933] to listener [com.xwiki.task.internal.TaskMacroUpdateEventListener@5282a915]
class java.lang.NullPointerException: null
    at com.xwiki.task.internal.TaskMacroUpdateEventListener.updateTaskPages(TaskMacroUpdateEventListener.java:133)
    at com.xwiki.task.internal.TaskMacroUpdateEventListener.processEvent(TaskMacroUpdateEventListener.java:118)
    at com.xwiki.task.internal.AbstractTaskEventListener.onEvent(AbstractTaskEventListener.java:100)
    at org.xwiki.observation.internal.DefaultObservationManager.notify(DefaultObservationManager.java:320)
    at org.xwiki.observation.internal.DefaultObservationManager.notify(DefaultObservationManager.java:285)
    at com.xpn.xwiki.XWiki.beforeSave(XWiki.java:2015)
    at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:2074)
    at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:2001)
    at com.xpn.xwiki.XWiki.restoreFromRecycleBin(XWiki.java:7543)
    at org.xwiki.refactoring.internal.DefaultModelBridge.restoreDeletedDocument(DefaultModelBridge.java:522)
    at org.xwiki.refactoring.internal.job.RestoreJob.handleDeletedDocuments(RestoreJob.java:56)
    at org.xwiki.refactoring.internal.job.AbstractDeletedDocumentsJob.runInternal(AbstractDeletedDocumentsJob.java:89)
    at org.xwiki.job.AbstractJob.runInContext(AbstractJob.java:246)
    at org.xwiki.job.AbstractJob.run(AbstractJob.java:223)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:829)