Server stall: NoClassDefFoundError: com/mojang/realmsclient/gui/ChatFormatting

[RisingInIris2017]

Versions

Mod version:

animalnet-v1.12.2+b3

Forge version:

forge-1.12.2-14.23.5.2847

Singleplayer or Multiplayer:

Multiplayer, using CatServer-0c9a30f-universal

Installed mods:

Description of the problem

How to reproduce:

1. Catch some mobs.
2. Trying to release them by keeping right-clicking with a Caught Mob item in the main hand.
3. Nothing is released, but server stalls.

Before the moment the server reported "stopped responding", there were always log reports like these below, keeping occurring:

[18:34:22] [Server thread/FATAL] [VanillaFix]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NoClassDefFoundError: com/mojang/realmsclient/gui/ChatFormatting
at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_241]
...
Caused by: java.lang.NoClassDefFoundError: com/mojang/realmsclient/gui/ChatFormatting
at me.marnic.animalnet.common.item.ItemCaughtEntity.sendError(ItemCaughtEntity.java:164) ~[ItemCaughtEntity.class:?]
at me.marnic.animalnet.common.item.ItemCaughtEntity.onItemUse(ItemCaughtEntity.java:134) ~[ItemCaughtEntity.class:?]
at net.minecraftforge.common.ForgeHooks.onPlaceItemIntoWorld(ForgeHooks.java:890) ~[ForgeHooks.class:git-CatServer-1.12.2-0c9a30f]
at net.minecraft.item.ItemStack.onItemUse(ItemStack.java:213) ~[aip.class:?]
at net.minecraft.server.management.PlayerInteractionManager.processRightClickBlock(PlayerInteractionManager.java:598) ~[or.class:?]
at net.minecraft.network.NetHandlerPlayServer.processTryUseItemOnBlock(NetHandlerPlayServer.java:1128) ~[pa.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.processPacket(SourceFile:55) ~[ma.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.processPacket(SourceFile:11) ~[ma.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[hv$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_241]
at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_241]
at net.minecraft.util.Util.runTask(Util.java:529) ~[h.class:?]
... 5 more

Link to full stall log:

latest.log 1: https://paste.ubuntu.com/p/4QzMb3QJZn/
latest.log 2: https://paste.ubuntu.com/p/D52q3g2XXT/

I do not know what did happen, but I think it is helpful to report this to you.
I hope to get your help sincerely.
Look forward to your reply!
Thanks in advance!

[MrMarnic]

I will try to fix this.