Lottery+ error

08.04 08:24:19 [Server] SEVERE at net.minecraft.server.v1_5_R2.ThreadServerApplication.run(SourceFile:573)
08.04 08:24:19 [Server] SEVERE at net.minecraft.server.v1_5_R2.MinecraftServer.run(MinecraftServer.java:409)
08.04 08:24:19 [Server] SEVERE at net.minecraft.server.v1_5_R2.MinecraftServer.q(MinecraftServer.java:476)
08.04 08:24:19 [Server] SEVERE at net.minecraft.server.v1_5_R2.DedicatedServer.r(DedicatedServer.java:226)
08.04 08:24:19 [Server] SEVERE at net.minecraft.server.v1_5_R2.DedicatedServer.am(DedicatedServer.java:261)
08.04 08:24:19 [Server] SEVERE at org.bukkit.craftbukkit.v1_5_R2.CraftServer.dispatchServerCommand(CraftServer.java:512)
08.04 08:24:19 [Server] SEVERE at org.bukkit.craftbukkit.v1_5_R2.CraftServer.dispatchCommand(CraftServer.java:523)
08.04 08:24:19 [Server] SEVERE at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:189)
08.04 08:24:19 [Server] SEVERE at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
08.04 08:24:19 [Server] SEVERE at com.randude14.lotteryplus.command.CommandManager.onCommand(CommandManager.java:53)
08.04 08:24:19 [Server] SEVERE at com.randude14.lotteryplus.command.GuiCreatorCommand.execute(GuiCreatorCommand.java:13)
08.04 08:24:19 [Server] SEVERE at com.randude14.lotteryplus.LotteryPlus.openGui(LotteryPlus.java:285)
08.04 08:24:19 [Server] SEVERE at com.randude14.lotteryplus.gui.MainFrame.<init>(MainFrame.java:39)
08.04 08:24:19 [Server] SEVERE at javax.swing.JFrame.<init>(JFrame.java:180)
08.04 08:24:19 [Server] SEVERE at java.awt.Frame.<init>(Frame.java:385)
08.04 08:24:19 [Server] SEVERE at java.awt.Frame.<init>(Frame.java:420)
08.04 08:24:19 [Server] SEVERE at java.awt.Window.<init>(Window.java:535)
08.04 08:24:19 [Server] SEVERE at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:207)
08.04 08:24:19 [Server] INFO No X11 DISPLAY variable was set, but this program performed an operation which requires it.
08.04 08:24:19 [Server] SEVERE java.awt.HeadlessException:
08.04 08:24:19 [Server] INFO - Exception caught while executing this command.