Crash occurs when the chisel breaks mid-stack (with cobblestone). This is the second occurrence this evening in the modpack Modern Skyblock 2. I'm assuming this isn't a Chisel API version issue since the item being chiseled is a vanilla item.

Please let me know if I can provide any further info.

Crash Report: crash-2017-12-18_20.04.15-client.txt
Forge version: forge-14.23.1.12566
MC Version: 1.12.2
Chisel Version: Chisel-MC1.12-0.1.0.23
Modpack: Modern Skyblock 2 v, 2.7.3.2

Duplicate of #603