1.12.2 Slime Monster Reanimation Crashes Game

General Information

Describe the bug:

Whenever you perform the monster reanimation ritual for slimes in Minecraft 1.12.2 the altar glows purple for a few seconds and then crashes the whole game.

To Reproduce:

Set up altar with mundane and attuning stones surrounding the altar
Put incense burners with one containing a nether wart and the other coal and light with flint and steel (I have lit both before and after next step)
Place three slime balls on the altar and left click with no item in hand (this causes the purple light from altar and then game crash).

Expected behavior:

It is expected that a slime would spawn after the purple glowing light disappears.

Environment Versions

I have only tried to do this with minecraft 1.12.2 (RootsClassic-1.12.2-1.1.5) and the hexxit modpack installed as well. I have not tried any other versions.

Mystic Mods Versions

I do not believe I have any installed as far as I can see should they contain the word mystic in the name

Other Versions:

Conflicting mod (if regarding mod integration):
Other mods you think could cause issues:
Forge: CurseForge
Minecraft: 1.12.2
Modpack (if available): Hexxit I have a couple backpack mods, minihud, etc. installed as well, but none that I believe would conflict.

Logging Information

Please Use gist, paste.ee, pastebin or some other log sharing service

Crash Report (if available):

https://gist.github.com/ECubeD1/60a6340c306deef56282bdacebbf504e (I believe I did this right) Latest Log (if necessary):

Additional Information

Screenshots (if available):

Additional context (optional):

I can summon every other mob, but a slime crashes it. I have tried out in the open and below y = 39. I have also tried summoning them both above and below y = 39 in a slime chunk and with all other entities killed as well as them being there

MysticMods / Roots