It looks like we are talking only of the rare case where the AppMaster dies somehow, right? For failed jobs, the 'Tracking UI' column looks like it is set correctly to point to the job history page for that job.
In the case when a job fails, it is the AM that sends the unregister event to the RM telling the RM to change the tracking URL. However, in the use case we are addressing, the AM has died. I've looked into alterative ways to get the job history URL for a job in this case, but I think it would involve having other daemons try to recreate the AM's unregister event.
To me, since this is a narrow use case, I think it is sufficient to just "null-out" the tracking URL, which will cause the scheduler UI to put UNASSIGNED in the 'Tracking UI' column, which will not be a link.