I was riding a horse into newly generated land when the crash occurred. I think the horse outran the world generator, because I'd been getting pauses in the animation for several minutes prior to the crash that didn't happen when riding through existing chunks.

Then it crashed with the attached dump. This may be similar to other crash dumps with this label, but it's hard to tell from the description, so I'm opening it as a separate case.

Hardcore mode, single player