Voxels v1.0.8
Spark's Hammers v1.6.3.1
Forge 1.10.2-2254
I got this crash after clicking on this mod's creative tab. No hammers were displaying in the tab before it crashed, only the hammer crafting table and other items.
Crash Report

Unfortunately I couldn't re-create this using the same mods.
Tbh, I think this is an issue with Voxels anyway, but since their code is not open source I can't even confirm that. There's nothing I can do over here, so I strongly suggest posting this on their issues and see what they say.

I'll close this issue for now, but we can re-open this if it's confirmed this is an issue in my mod.

Ok, thanks