star wars mod calling X11 window?

[00:40:03] [Server thread/ERROR] [FML]: There was a critical exception handling a packet on channel FML
java.awt.HeadlessException:
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
        at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:207) ~[?:1.8.0_05]
        at java.awt.Window.<init>(Window.java:536) ~[?:1.8.0_05]
        at java.awt.Frame.<init>(Frame.java:420) ~[?:1.8.0_05]
        at java.awt.Frame.<init>(Frame.java:385) ~[?:1.8.0_05]
        at javax.swing.JFrame.<init>(JFrame.java:181) ~[?:1.8.0_05]
        at de.maggicraft.starwarsmod.wiki.frames.FrameUpdate.<init>(FrameUpdate.java:23) ~[FrameUpdate.class:?]
        at de.maggicraft.starwarsmod.MaggiEventHandler.checkUpdate(MaggiEventHandler.java:25) ~[MaggiEventHandler.class:?]
        at cpw.mods.fml.common.eventhandler.ASMEventHandler_362_MaggiEventHandler_checkUpdate_PlayerLoggedInEvent.invoke(.dynamic) ~[?:?]
        at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:54) ~[ASMEventHandler.class:?]
        at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:139) ~[EventBus.class:?]
        at cpw.mods.fml.common.FMLCommonHandler.firePlayerLoggedIn(FMLCommonHandler.java:550) ~[FMLCommonHandler.class:?]
        at net.minecraft.server.management.ServerConfigurationManager.a(ServerConfigurationManager.java:180) ~[oi.class:?]
        at cpw.mods.fml.common.network.handshake.NetworkDispatcher.completeServerSideConnection(NetworkDispatcher.java:173) ~[NetworkDispatcher.class:?]
        at cpw.mods.fml.common.network.handshake.NetworkDispatcher.completeHandshake(NetworkDispatcher.java:446) ~[NetworkDispatcher.class:?]
        at cpw.mods.fml.common.network.internal.HandshakeCompletionHandler.channelRead0(HandshakeCompletionHandler.java:17) ~[HandshakeCompletionHandler.class:?]
        at cpw.mods.fml.common.network.internal.HandshakeCompletionHandler.channelRead0(HandshakeCompletionHandler.java:11) ~[HandshakeCompletionHandler.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.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103) ~[MessageToMessageDecoder.class:?]
        at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.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.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) ~[EmbeddedChannel.class:?]
        at cpw.mods.fml.common.network.internal.FMLProxyPacket.func_148833_a(FMLProxyPacket.java:77) [FMLProxyPacket.class:?]
        at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212) [ej.class:?]
        at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165) [nc.class:?]
        at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659) [MinecraftServer.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:334) [lt.class:?]
        at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685) [li.class:?]