Bukkit

What steps will reproduce the problem?
1.Load plugin on 1.7 Server
2.Change someone's gamemode

What is the expected output? What do you see instead?
Because of what I set in my config, the inventories should change, but they stayed the same instead.

What version of the product are you using?
1.6

Do you have an error log of what happened?
[18:50:54 ERROR]: Could not pass event PlayerGameModeChangeEvent to RestrictCreative v1.6
org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:427) ~[minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at org.bukkit.craftbukkit.v1_7_R1.entity.CraftPlayer.setGameMode(CraftPlayer.java:625) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at com.earth2me.essentials.PlayerExtension.setGameMode(PlayerExtension.java) [Essentials.jar:?]
    at com.earth2me.essentials.commands.Commandgamemode.run(Commandgamemode.java:76) [Essentials.jar:?]
    at com.earth2me.essentials.commands.EssentialsCommand.run(EssentialsCommand.java:135) [Essentials.jar:?]
    at com.earth2me.essentials.Essentials.onCommandEssentials(Essentials.java:505) [Essentials.jar:?]
    at com.earth2me.essentials.Essentials.onCommand(Essentials.java:372) [Essentials.jar:?]
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:192) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at org.bukkit.craftbukkit.v1_7_R1.CraftServer.dispatchCommand(CraftServer.java:542) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.PlayerConnection.handleCommand(PlayerConnection.java:925) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.PlayerConnection.a(PlayerConnection.java:805) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.PacketPlayInChat.a(PacketPlayInChat.java:28) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.PacketPlayInChat.handle(PacketPlayInChat.java:47) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:146) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:651) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:250) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:541) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:453) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
Caused by: java.lang.NoClassDefFoundError: org/bukkit/craftbukkit/v1_6_R3/inventory/CraftItemStack
    at net.endercraftbuild.inventories.InvManager.saveInventory(InvManager.java:46) ~[?:?]
    at net.endercraftbuild.inventories.InvManager.onPlayerGameModeChange(InvManager.java:32) ~[?:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_45]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_45]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_45]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_45]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425) ~[minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    ... 23 more
Caused by: java.lang.ClassNotFoundException: org.bukkit.craftbukkit.v1_6_R3.inventory.CraftItemStack
    at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:70) ~[minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:53) ~[minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425) ~[?:1.7.0_45]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358) ~[?:1.7.0_45]
    at net.endercraftbuild.inventories.InvManager.saveInventory(InvManager.java:46) ~[?:?]
    at net.endercraftbuild.inventories.InvManager.onPlayerGameModeChange(InvManager.java:32) ~[?:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_45]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_45]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_45]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_45]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425) ~[minecraft_server.jar:git-Bukkit-1.6.4-R2.0-23-ge8eb325-b2941jnks]
    ... 23 more

Please provide any additional information below.
I haven't tested anything else yet.