Please help me, I don't know what this means, it happens every time I connect to the server and click disconnect quickly

Then the server goes down and generates this Crash report

[23:44:08] [Server thread/INFO] [net.minecraft.network.NetHandlerPlayServer]: Meidde lost connection: Disconnected
[23:44:08] [Server thread/ERROR] [FML]: Exception caught during firing event net.minecraftforge.fml.common.gameevent.PlayerEvent$PlayerLoggedOutEvent@96a8c8f:
java.lang.NullPointerException: null
    at deathtags.core.events.EventCommon.onPlayerLeave(EventCommon.java:67) ~[EventCommon.class:?]
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_1140_EventCommon_onPlayerLeave_PlayerLoggedOutEvent.invoke(.dynamic) ~[?:?]
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:96) ~[ASMEventHandler.class:?]
    at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:186) [EventBus.class:?]
    at net.minecraftforge.fml.common.FMLCommonHandler.firePlayerLoggedOut(FMLCommonHandler.java:573) [FMLCommonHandler.class:?]
    at net.minecraft.server.management.PlayerList.func_72367_e(PlayerList.java:526) [pl.class:?]
    at net.minecraft.server.management.PlayerList.disconnect(PlayerList.java:519) [pl.class:?]
    at net.minecraft.network.NetHandlerPlayServer.func_147231_a(NetHandlerPlayServer.java:1287) [pa.class:?]
    at net.minecraft.network.NetworkManager.func_179293_l(NetworkManager.java:473) [gw.class:?]
    at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:232) [oz.class:?]
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:922) [MinecraftServer.class:?]
    at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:461) [nz.class:?]
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:778) [MinecraftServer.class:?]
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:624) [MinecraftServer.class:?]
    at java.lang.Thread.run(Thread.java:748) [?:1.8.0_311]

 

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