Infos:
MC: 1.12.2
Forge: 14.23.5.2854

Discription:
While "The Twilight Forest - Mod" installed, come near a Hydra Cave (Structure in TW Forest, spawns a Boss Mob from a spawner) the game crashes.
Hydra Cave Mob: https://ftb.gamepedia.com/Hydra

Reproduce:

• Teleport to DIM 7
• Search for a Hydra cave and come near
• When Mob try to spawn -> Crash

Log:
Latest Log: https://pastebin.com/mzbnkc9L
Crash Report (Vanilla Fix): https://pastebin.com/qc1Zv7tL

Thought's:

• Maybe the Hydra starts an indirect damage mechanic
  -- So it is the same Bug as "[BUG] Splash Potion on GoG Mobs #14"

Note:

• The crash happens instantly, I was not able to see the mob

I can't view the picture (Google Photos, 403 Forbidden), can you try uploading it directly to GitHub?

(Thanks for your patience, been busy)
Huh... Potentially related to #13 I think. Either way, adding a simple check ought to fix the problem at least.

Picture Update, when needed:
https://ftb.gamepedia.com/Hydra

I know Twilight Forest's Hydra is made of multiple parts. Like the head are separate entities from the body. That could be what's causing the problem, as TF probably handles resource location for multi part mobs in a unique way that differs from my approach of looking them up.

Commit 8e13ad0 should fix this.