A huge 30x30 pit of nothing just appeared

An impassable but viewable pit of nothing (appears as a black hole) that goes down to the bottom of the world.

What I expected to happen was...:
I thought that re-logging would eliminate this, but it has remained.

What actually happened was...:
Not sure if this is a bug or more of a corruption of the game somehow.

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
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