Unsupported Optifine Version When Using Latest

[Desoroxxx]

Version Information

Minecraft version: 1.12.2
Forge version: 14.23.5.2860
Other mods (if applicable):
Optifine: preview_OptiFine_1.12.2_HD_U_G6_pre1

Steps to reproduce:

1. Launch Minecraft
2. Look at the log
3. See error

Expected Behavior:
Since 1.12.2 is pretty much dead to Optifine eyes, it also modifies pretty much nothing, so we can assume the 1.12.2 G6 preview to be the latest stable Optifine version so CC should recognize.

Actual Behavior:
CC does not recognize it and throws an error

Log/Console

[NotStirred]

G5 is the last stable version, G6 is a preview version