You should provide the whole serverlog. Or at least the Relevant pieces.
Try a previous Build.
Also, if you dont need to generate new Terrain, and/or rely on Sapling Ressources/MobSpawning in Custom Biomes, you can also just disable TC.
If you get a working version of TC for 1.12 it should work the same as before. You wont need a new world.
You dont get new blocks in your world though.
Dont be impatient, People dont sleep in front of their PC just to answer you questions.