Need null check here. getMapping(IResource) can return null for inaccessible projects (closed).

java.lang.NullPointerException
	at org.eclipse.egit.core.synchronize.GitSubscriberMergeContext$2.resourceChanged(GitSubscriberMergeContext.java:70)
	at org.eclipse.core.internal.events.NotificationManager$1.run(NotificationManager.java:291)
	at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
	at org.eclipse.core.internal.events.NotificationManager.notify(NotificationManager.java:285)
	at org.eclipse.core.internal.events.NotificationManager.broadcastChanges(NotificationManager.java:149)
	at org.eclipse.core.internal.resources.Workspace.broadcastPostChange(Workspace.java:395)
	at org.eclipse.core.internal.resources.Workspace.endOperation(Workspace.java:1530)
	at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:45)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)