[11:10:16 ERROR]: Could not pass event CraftItemEvent to GravityGun v1.0
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:305) ~[spigot.jar:git-Spigot-13716d9-0899683]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-13716d9-0899683]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot.jar:git-Spigot-13716d9-0899683]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot.jar:git-Spigot-13716d9-0899683]
        at net.minecraft.server.v1_8_R1.PlayerConnection.a(PlayerConnection.java:1586) [spigot.jar:git-Spigot-13716d9-0899683]
        at net.minecraft.server.v1_8_R1.PacketPlayInWindowClick.a(SourceFile:31) [spigot.jar:git-Spigot-13716d9-0899683]
        at net.minecraft.server.v1_8_R1.PacketPlayInWindowClick.a(SourceFile:9) [spigot.jar:git-Spigot-13716d9-0899683]
        at net.minecraft.server.v1_8_R1.PacketHandleTask.run(SourceFile:13) [spigot.jar:git-Spigot-13716d9-0899683]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_25]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_25]
        at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:683) [spigot.jar:git-Spigot-13716d9-0899683]
        at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:316) [spigot.jar:git-Spigot-13716d9-0899683]
        at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:623) [spigot.jar:git-Spigot-13716d9-0899683]
        at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java:526) [spigot.jar:git-Spigot-13716d9-0899683]
        at java.lang.Thread.run(Thread.java:745) [?:1.8.0_25]
Caused by: java.lang.NullPointerException
        at de.LabyStudio.main.GravityGun.onCraft(GravityGun.java:86) ~[?:?]
        at sun.reflect.GeneratedMethodAccessor244.invoke(Unknown Source) ~[?:?]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_25]
        at java.lang.reflect.Method.invoke(Method.java:483) ~[?:1.8.0_25]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301) ~[spigot.jar:git-Spigot-13716d9-0899683]
        ... 14 more