Problem direwolf20 server crash

[ben-el]

the server is crashing everytime i lunching him
this is the crash report
thanks for helping
---- Minecraft Crash Report ----
// Don't be sad, have a hug! <3

Time: 19:58 06/08/14
Description: Exception in server tick loop

java.lang.NullPointerException
at net.minecraft.network.packet.Packet.func_73271_a(Packet.java:199)
at mcp.mobius.opis.data.holders.newtypes.DataStringUpdate.writeToStream(DataStringUpdate.java:24)
at mcp.mobius.opis.network.packets.server.NetDataValue.create(NetDataValue.java:46)
at mcp.mobius.opis.data.managers.StringCache.getIndex(StringCache.java:54)
at mcp.mobius.opis.data.holders.newtypes.CachedString.<init>(CachedString.java:33)
at mcp.mobius.opis.data.holders.newtypes.DataDimension.fill(DataDimension.java:42)
at mcp.mobius.opis.events.OpisServerTickHandler.tickEnd(OpisServerTickHandler.java:111)
at cpw.mods.fml.common.SingleIntervalHandler.tickEnd(SingleIntervalHandler.java:34)
at cpw.mods.fml.common.FMLCommonHandler.tickEnd(FMLCommonHandler.java:141)
at cpw.mods.fml.common.FMLCommonHandler.onPostServerTick(FMLCommonHandler.java:274)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:622)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)

 

[Connor Gavitt]

Try disabling opis and only use it when you absolutely have to.

 

[ben-el]

Try disabling opis and only use it when you absolutely have to.

how do i do it?