Help for an error?

since some days i have this error, but it’s not my plugin, or i don’t see it…
can you help me because my server crash!!
it’s happends after a player logout and login after!!!
[spoil=“error”]
[19:23:17] [Server thread/INFO]: Diabl091p lost connection: TextComponent{text=‘Internal server error’, siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
[19:23:17] [Server thread/ERROR]: Encountered an unexpected exception
java.lang.NoSuchFieldError: worldObj
at net.minecraft.entity.player.EntityPlayer.func_70999_a(EntityPlayer.java:93) ~[ahd.class:?]
at net.minecraft.entity.player.EntityPlayerMP.func_70999_a(EntityPlayerMP.java:648) ~[qw.class:?]
at net.minecraft.entity.player.EntityPlayerMP.func_71123_m(EntityPlayerMP.java:916) ~[qw.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_147231_a(NetHandlerPlayServer.java:701) ~[rj.class:?]
at net.minecraft.network.NetworkManager.func_179293_l(NetworkManager.java:403) ~[gr.class:?]
at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:185) ~[rc.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:727) ~[MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:364) ~[po.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:598) ~[MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:478) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_60]

[/spoil]

There was a thread with this last week

I need to get @mumfrey or someone who knows how to fix it ASAP.