打开ess的config
看看
找到allow-silent-join-quit: false 改为true (启用上、下线提示)

先吧ess文件的配置备份然后再删掉让系统重新生成看看有没有

这个明明是允许静默上下线

[22:10:11] [Server thread/INFO]: Mokou lost connection: Disconnected
[22:10:11] [Server thread/WARN]: [Essentials] Task #981 for Essentials vTeamCity generated an exception
java.lang.NullPointerException
        at com.earth2me.essentials.xmpp.XMPPManager.updatePresence(XMPPManager.java:171) ~[?:?]
        at com.earth2me.essentials.xmpp.EssentialsXMPP.updatePresence(EssentialsXMPP.java:123) ~[?:?]
        at com.earth2me.essentials.xmpp.EssentialsXMPPPlayerListener$2.run(EssentialsXMPPPlayerListener.java:59) ~[?:?]
        at org.bukkit.craftbukkit.v1_9_R2.scheduler.CraftTask.run(CraftTask.java:71) ~[spigot-1.9.4.jar:git-Spigot-798f32d-0cd0397]
        at org.bukkit.craftbukkit.v1_9_R2.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:350) [spigot-1.9.4.jar:git-Spigot-798f32d-0cd0397]
        at net.minecraft.server.v1_9_R2.MinecraftServer.D(MinecraftServer.java:734) [spigot-1.9.4.jar:git-Spigot-798f32d-0cd0397]
        at net.minecraft.server.v1_9_R2.DedicatedServer.D(DedicatedServer.java:399) [spigot-1.9.4.jar:git-Spigot-798f32d-0cd0397]
        at net.minecraft.server.v1_9_R2.MinecraftServer.C(MinecraftServer.java:665) [spigot-1.9.4.jar:git-Spigot-798f32d-0cd0397]
        at net.minecraft.server.v1_9_R2.MinecraftServer.run(MinecraftServer.java:564) [spigot-1.9.4.jar:git-Spigot-798f32d-0cd0397]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_91]