Exception

06:43:54 [SEVERE] java.lang.NullPointerException
06:43:54 [SEVERE] 	at java.util.concurrent.ConcurrentHashMap.containsValue(ConcurrentHashMap.java:827)
06:43:54 [SEVERE] 	at com.Balor.bukkit.GiftPost.GiftPostWorker.setDefaultChest(GiftPostWorker.java:303)
06:43:54 [SEVERE] 	at com.Balor.bukkit.GiftPost.GiftPostWorker.setDefaultChest(GiftPostWorker.java:299)
06:43:54 [SEVERE] 	at com.Balor.commands.SetChest.execute(SetChest.java:49)
06:43:54 [SEVERE] 	at com.Balor.bukkit.GiftPost.GiftPost.onCommand(GiftPost.java:275)
06:43:54 [SEVERE] 	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:35)
06:43:54 [SEVERE] 	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:129)
06:43:54 [SEVERE] 	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:320)
06:43:54 [SEVERE] 	at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:713)
06:43:54 [SEVERE] 	at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:677)
06:43:54 [SEVERE] 	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:670)
06:43:54 [SEVERE] 	at net.minecraft.server.Packet3Chat.a(Packet3Chat.java:33)
06:43:54 [SEVERE] 	at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
06:43:54 [SEVERE] 	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:85)
06:43:54 [SEVERE] 	at net.minecraft.server.NetworkListenThread.a(SourceFile:105)
06:43:54 [SEVERE] 	at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:451)
06:43:54 [SEVERE] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:361)
06:43:54 [SEVERE] 	at net.minecraft.server.ThreadServerApplication.run(SourceFile:422)