Sky renders through walls when using fog

Partner Rank: 2

Verification builds: 1.17.2, 1.17.20
Regression builds: This has always been an issue

Summary: When using custom fog with /fog, your render distance is reduced, and when this prevents a wall from rendering, you can see through to the sky, which is a completely different color which completely ruins the effect.

Impact: Fog looks so bad we'd rather just not use it.

Repro Steps:

1. Download and open the attached world. You should already be in a black concrete box.
2. Press the button on the right labelled "apply fog"
3. Wait for the fog to kick in

Expected Results: The back wall becomes pure green.

Observed Results: After the fog gets close enough, part of the green disappears, revealing ugly blocks that show the sky behind.

Screenshots/Videos attached: Yes

Notes: After observing the issue, press the button on the left labelled "see what it should look like." This places some structure void blocks near the discontinuity that seems to temporarily fix it. That is our desired appearance.