Sometimes the issue cache has junk in it.
Sometimes the issue cache has junk in it.

I got this to happen after some issues had been detected on the live map,
then starting the intro walkthrough (which replaces the graph).

No time now to dig into the root cause, but this might make the problem go
away so the tutorial doesn't get too weird.

openstreetmap/iD,morray/iD,morray/iD,openstreetmap/iD,openstreetmap/iD