[17:00:54] [Netty IO #2/ERROR]: Could not pass event ServerListPingEvent to Essentials v2.0.1-b429
org.bukkit.event.EventException
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:338) ~[JavaPluginLoader$1.class:1.7.10-1614.58]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[RegisteredListener.class:1.7.10-1614.58]
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:507) [SimplePluginManager.class:1.7.10-1614.58]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:492) [SimplePluginManager.class:1.7.10-1614.58]
at net.minecraft.server.network.NetHandlerStatusServer.func_147312_a(NetHandlerStatusServer.java:87) [nq.class:?]
at net.minecraft.network.status.client.C00PacketServerQuery.func_148833_a(SourceFile:25) [kj.class:?]
at net.minecraft.network.status.client.C00PacketServerQuery.func_148833_a(SourceFile:8) [kj.class:?]
at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:137) [ej.class:?]
at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:353) [ej.class:?]
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:98) [SimpleChannelInboundHandler.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:173) [ByteToMessageDecoder.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:173) [ByteToMessageDecoder.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
at com.comphenix.protocol.compat.netty.independent.NettyChannelInjector$4.channelRead(NettyChannelInjector.java:280) [ProtocolLib-v1_7_R4-3.6.4.jar:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:173) [ByteToMessageDecoder.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
at io.netty.handler.timeout.ReadTimeoutHandler.channelRead(ReadTimeoutHandler.java:149) [ReadTimeoutHandler.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:785) [DefaultChannelPipeline.class:?]
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:100) [AbstractNioByteChannel$NioByteUnsafe.class:?]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:480) [NioEventLoop.class:?]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:447) [NioEventLoop.class:?]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:341) [NioEventLoop.class:?]
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:101) [SingleThreadEventExecutor$2.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_102]
Caused by: java.lang.UnsupportedOperationException
at org.bukkit.event.server.ServerListPingEvent.iterator(ServerListPingEvent.java:140) ~[ServerListPingEvent.class:1.7.10-1614.58]
at com.earth2me.essentials.EssentialsServerListener.onServerListPing(EssentialsServerListener.java:22) ~[?:?]
at sun.reflect.GeneratedMethodAccessor360.invoke(Unknown Source) ~[?:?]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_102]
at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_102]
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:334) ~[JavaPluginLoader$1.class:1.7.10-1614.58]
... 33 more

I don't know but since I updated Essentials to a devbuild, I have this error too.
Following plugin has problems since i updated all my servers' essentialsx
Bungeeserversigns (dev knows that)
Bungeeonlinetime
Bungeeweb
Only error from Essentials but its mysterious that this has a problem since i has updated Essentials...

i've downgrade to build 403 and all plugins works fine and no errors :)

Related to #868

Update to latest build.