Exception in server tick loop

[GT86]

---- Minecraft Crash Report ----

WARNING: coremods are present:
  MDCore (RewardDrops-0.3b (1).jar)
  MixinCoreMod (TileEntityBell-mixin-1.3.2.jar)
  PCCore (AdminPC-0.4.jar)
  SpongeCoremod (spongeforge-1.12.2-2838-7.1.8.jar)
Contact their authors BEFORE contacting forge

// Daisy, daisy...

Time: 3/16/20 9:40 PM
Description: Exception in server tick loop

java.lang.NullPointerException: Exception in server tick loop
	at io.netty.channel.ChannelOutboundBuffer.addMessage(ChannelOutboundBuffer.java:117)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.write(AbstractChannel.java:810)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.write(DefaultChannelPipeline.java:1291)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:816)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:723)
	at net.minecraftforge.fml.common.network.FMLOutboundHandler.write(FMLOutboundHandler.java:358)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:816)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:723)
	at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:111)
	at io.netty.handler.codec.MessageToMessageCodec.write(MessageToMessageCodec.java:116)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:816)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:723)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:704)
	at io.netty.channel.DefaultChannelPipeline.write(DefaultChannelPipeline.java:1017)
	at io.netty.channel.AbstractChannel.write(AbstractChannel.java:286)
	at io.netty.channel.embedded.EmbeddedChannel.writeOutbound(EmbeddedChannel.java:341)
	at net.minecraftforge.fml.common.network.FMLEmbeddedChannel.generatePacketFrom(FMLEmbeddedChannel.java:72)
	at net.minecraftforge.fml.common.network.internal.FMLNetworkHandler.getEntitySpawningPacket(FMLNetworkHandler.java:134)
	at net.minecraft.entity.EntityTrackerEntry.func_151260_c(EntityTrackerEntry.java:501)
	at net.minecraft.entity.EntityTrackerEntry.func_73117_b(EntityTrackerEntry.java:380)
	at net.minecraft.entity.EntityTracker.func_72788_a(EntityTracker.java:313)
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:779)
	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397)
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
	at java.lang.Thread.run(Thread.java:748)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Server thread
Stacktrace:
	at io.netty.channel.ChannelOutboundBuffer.addMessage(ChannelOutboundBuffer.java:117)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.write(AbstractChannel.java:810)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.write(DefaultChannelPipeline.java:1291)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:816)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:723)
	at net.minecraftforge.fml.common.network.FMLOutboundHandler.write(FMLOutboundHandler.java:358)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:816)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:723)
	at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:111)
	at io.netty.handler.codec.MessageToMessageCodec.write(MessageToMessageCodec.java:116)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:816)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:723)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:704)
	at io.netty.channel.DefaultChannelPipeline.write(DefaultChannelPipeline.java:1017)
	at io.netty.channel.AbstractChannel.write(AbstractChannel.java:286)
	at io.netty.channel.embedded.EmbeddedChannel.writeOutbound(EmbeddedChannel.java:341)
	at net.minecraftforge.fml.common.network.FMLEmbeddedChannel.generatePacketFrom(FMLEmbeddedChannel.java:72)
	at net.minecraftforge.fml.common.network.internal.FMLNetworkHandler.getEntitySpawningPacket(FMLNetworkHandler.java:134)
	at net.minecraft.entity.EntityTrackerEntry.func_151260_c(EntityTrackerEntry.java:501)
	at net.minecraft.entity.EntityTrackerEntry.func_73117_b(EntityTrackerEntry.java:380)
	at net.minecraft.entity.EntityTracker.func_72788_a(EntityTracker.java:313)

-- Sponge PhaseTracker --
Details:
	Phase Stack: [Empty stack]
Stacktrace:
	at net.minecraft.server.MinecraftServer.handler$onCrashReport$zjh000(MinecraftServer.java:4721)
	at net.minecraft.server.MinecraftServer.func_71230_b(MinecraftServer.java:889)
	at net.minecraft.server.dedicated.DedicatedServer.func_71230_b(DedicatedServer.java:371)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:558)
	at java.lang.Thread.run(Thread.java:748)

-- System Details --
Details:
	Minecraft Version: 1.12.2
	Operating System: Linux (amd64) version 4.15.0-88-generic
	Java Version: 1.8.0_242, Private Build
	Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Private Build
	Memory: 16958222856 bytes (16172 MB) / 26843545600 bytes (25600 MB) up to 26843545600 bytes (25600 MB)
	JVM Flags: 12 total; -Xms25G -Xmx25G -XX:+UseG1GC -XX:+UnlockExperimentalVMOptions -XX:MaxGCPauseMillis=100 -XX:+DisableExplicitGC -XX:TargetSurvivorRatio=90 -XX:G1NewSizePercent=50 -XX:G1MaxNewSizePercent=80 -XX:G1MixedGCLiveThresholdPercent=50 -XX:+AlwaysPreTouch -XX:+ParallelRefProcEnabled
	IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
	FML: MCP 9.42 Powered by Forge 14.23.5.2847 153 mods loaded, 153 mods active
	States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored

 

I don't know how this happened, if there is a solution please tell me

[DaemonUmbra]

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Please update to a modern version of Minecraft to receive support.