It crashes onload:
crash-2017-06-30_17.50.29-client.txt

added complete crash, instead of the stack trace.

Please post the complete crash report, instead of the end of the log file

I'm also seeing the same error in Forge versions *.2380 through *.2387

Currently testing with *.2387 in the latest report below

fml-client-latest.log.txt

Remove OptiFine and try again.

Optifine was the culprit. Alas, version *.C3 also results in the same error halfway through the mod loading process.

On a side note, Just Enough Buttons also crashes but right after everything has loaded.

I can confirm actually additions works on clean 1.12 with latest forge.. Thanks for help:)