I've tested this, and it is Chisel causing this error, without it, the modpack I'm working on loads no problem. Adding it into the modpack produces the following error:

The game crashed whilst initializing game
Error: java.lang.NullPointerException: The validated object is null

Now I realize this is an Alpha Release for 1.12, and I'm not expecting it to be 100%, which is why I am reporting the issue, so it can be looked into.

Do you have a full crash log?

crash-2017-10-08_18.51.37-client.txt

There ya go.

Update/install CTM, it is required.