Failed to load mods: __crushing-industry__/api.lua:69: attempt to index field 'molten-crushed-ore-productivity' (a nil value) stack traceback: __crushing-industry__/api.lua:69: in function 'add_molten_productivity' ...-tweaks__/k2so-tweaks/patches/mods/crushing-industry.lua:68: in function 'on_data_final_fixes' __nulls-k2so-tweaks__/k2so-tweaks/util/patch.lua:88: in function 'do_data_final_fixes' __nulls-k2so-tweaks__/data-final-fixes.lua:29: in main chunk

What are your startup settings for both mods? I'm using the latest Crushing Industry without issue.

Crushing Industry: everything default except Concrete with iron sticks, Landfill from sand and Stone brick from sand are disabled.

Null's Tweaks: everything on default

I also have this issue.
Seems to be some incompatibility between this mod and Crushing Industry Tweaks and Mod Compat, as disabling either solves the crash.
It seems likely that CITMC removes or renames something, and then this fails.
CITMC has an explicit optional dependency on this mod, so maybe it should be fixed there?
I have confirmed that the issue occurs from an empty modlist enabling only space age, this mod, and CITMC.

After I reported it to CITMC, the mod author of that has fixed the issue on their side in version 1.13.6, at least for me.