Black squares and triangles in the end sky with low render distance

The bug

Black squares and triangles in the end sky with low render distance.

How to reproduce

1. Go to the End
2. Change render distance to either 4 or 5 chunks
3. Move around your camera, you will notice the sky is glitched

The reason

The background box of the end gets partially outside of the render distance (the black parts are where it's out of the render distance).