weird exception when trying to join server(1.12.2)

[SDUBZ]

all of the details are here: grim3212/grim-pack#114 (comment)

dummy core version: 2.4.112.0

[kabachuha]

Hello, @SDUBZ! The DummyCore and EC3 have been dropped by their author(see @Modbder 's contribution activity). I advise you to check their fork by @TheLMiffy1111.
https://github.com/TheLMiffy1111/DummyCoreUnofficial
https://github.com/TheLMiffy1111/EssentialCraft4Unofficial

[SDUBZ]

im using EssentialCraftUnofficial-4.8.112.3 and DummyCoreUnofficial-2.4.112.0 @artem226 the issue page came here