[21:48:47 ERROR]: Could not pass event InventoryClickEvent to PortableHorses v0.2.3
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:427) ~[spigot.jar:git-Spigot-1180]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-1180]
        at org.bukkit.plugin.TimedRegisteredListener.callEvent(TimedRegisteredListener.java:30) ~[spigot.jar:git-Spigot-1180]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:478) [spigot.jar:git-Spigot-1180]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:463) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.PlayerConnection.a(PlayerConnection.java:1357) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.PacketPlayInWindowClick.a(SourceFile:32) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.PacketPlayInWindowClick.handle(SourceFile:10) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:146) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:647) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:259) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:530) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:442) [spigot.jar:git-Spigot-1180]
        at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [spigot.jar:git-Spigot-1180]
Caused by: java.lang.IllegalArgumentException: Cannot drop a Null item.
        at org.apache.commons.lang.Validate.notNull(Validate.java:192) ~[spigot.jar:git-Spigot-1180]
        at org.bukkit.craftbukkit.v1_7_R1.CraftWorld.dropItem(CraftWorld.java:297) ~[spigot.jar:git-Spigot-1180]
        at com.norcode.bukkit.portablehorses.PortableHorses.onUnsaddled(PortableHorses.java:298) ~[?:?]
        at com.norcode.bukkit.portablehorses.PortableHorses.onSaddleEvent(PortableHorses.java:238) ~[?:?]
        at sun.reflect.GeneratedMethodAccessor99.invoke(Unknown Source) ~[?:?]
        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) ~[spigot.jar:git-Spigot-1180]
        ... 14 more