17:07:12 ERROR]: Could not pass event PlayerEditBookEvent to RealMail v0.2.8
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:305) ~[spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at org.bukkit.craftbukkit.v1_8_R2.event.CraftEventFactory.handleEditBookEvent(CraftEventFactory.java:846) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at net.minecraft.server.v1_8_R2.PlayerConnection.a(PlayerConnection.java:1981) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at net.minecraft.server.v1_8_R2.PacketPlayInCustomPayload.a(SourceFile:55) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at net.minecraft.server.v1_8_R2.PacketPlayInCustomPayload.a(SourceFile:8) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at net.minecraft.server.v1_8_R2.PlayerConnectionUtils$1.run(SourceFile:13) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) [?:1.7.0_71]
        at java.util.concurrent.FutureTask.run(FutureTask.java:262) [?:1.7.0_71]
        at net.minecraft.server.v1_8_R2.SystemUtils.a(SourceFile:60) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at net.minecraft.server.v1_8_R2.MinecraftServer.A(MinecraftServer.java:710) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at net.minecraft.server.v1_8_R2.DedicatedServer.A(DedicatedServer.java:368) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at net.minecraft.server.v1_8_R2.MinecraftServer.z(MinecraftServer.java:651) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at net.minecraft.server.v1_8_R2.MinecraftServer.run(MinecraftServer.java:554) [spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        at java.lang.Thread.run(Thread.java:745) [?:1.7.0_71]
Caused by: java.lang.NullPointerException
        at com.challengercity.plugins.realmail.RealMail$MailListener.onEditBook(RealMail.java:628) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_71]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_71]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_71]
        at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_71]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301) ~[spigot-1.8.3.jar:git-Spigot-1d14d5f-ba32592]
        ... 16 more