After adding Thaumcraft and Bables to the build path (#69). I went ahead and clicked the creative tab to see available materials and bam. Crash log: crash-2018-05-20_00.44.24-client.txt

This should be caused by the fact that the mappings used by my deobf jar on curseforge isn't the same as your dev environment.

Yeah thanks for pointing that out, I worked around it.
I removed the deobf jaopca jar and wrapup from the build path and used gradle on the normal file instead.

Added these to the dependencies section of build.gradle

    compile files ("gradlelibs/JAOPCA-1.12.2-2.2.6.83.jar")
    compile files ("gradlelibs/WrapUp-1.12-1.1.3.jar")

This still allows the mod to run with different mappings and no more crashes issue #69 still persists though.