task

[09:30:47 FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
    at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.7.0_75]
    at java.util.concurrent.FutureTask.get(FutureTask.java:188) ~[?:1.7.0_75]
    at net.minecraft.server.v1_8_R2.SystemUtils.a(SourceFile:61) [5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.MinecraftServer.A(MinecraftServer.java:710) [5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.DedicatedServer.A(DedicatedServer.java:368) [5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.MinecraftServer.z(MinecraftServer.java:651) [5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.MinecraftServer.run(MinecraftServer.java:554) [5.jar:git-Spigot-4c7d0c0-96c2c39]
    at java.lang.Thread.run(Thread.java:745) [?:1.7.0_75]
Caused by: java.lang.NullPointerException
    at net.minecraft.server.v1_8_R2.MerchantRecipeList.a(SourceFile:48) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.MerchantRecipeList.a(SourceFile:40) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.InventoryMerchant.h(InventoryMerchant.java:168) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.InventoryMerchant.setItem(InventoryMerchant.java:115) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.Slot.set(Slot.java:55) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.Container.clickItem(Container.java:285) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.PlayerConnection.a(PlayerConnection.java:1627) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.PacketPlayInWindowClick.a(SourceFile:31) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.PacketPlayInWindowClick.a(SourceFile:9) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at net.minecraft.server.v1_8_R2.PlayerConnectionUtils$1.run(SourceFile:13) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) ~[?:1.7.0_75]
    at java.util.concurrent.FutureTask.run(FutureTask.java:262) ~[?:1.7.0_75]
    at net.minecraft.server.v1_8_R2.SystemUtils.a(SourceFile:60) ~[5.jar:git-Spigot-4c7d0c0-96c2c39]
    ... 5 more