1.12.2's vulnerability is 61.55% of my satisfaction, but I released this cube vulnerability. It's the black one.It's a lot of loopholes

What I hope to happen is...
No black holes and no lowfps
What actually happened is...
At the end of the lowfps (at least <15fps), there appeared a black cube vulnerability, which was continuously generated.
**Steps to Reproduce:**
1. how to trigger a mistake here step by step
2. to a certain place
3. there is a bit of lowfps, FPS low
4. there is a black hole, the cube of the vulnerability generation
5. cubic loopholes are constantly emerging

This vulnerability has been detected since 12:30 in May 20, 2018, but I haven't entered the Bug Tracker yet, and I landed today.

This is too frightening!

The following screenshot can prove this point