Bukkit

[SEVERE] Could not pass event PlayerJoinEvent to HealthBarPlus
org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:303)
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:459)
    at net.minecraft.server.ServerConfigurationManager.c(ServerConfigurationManager.java:132)
    at net.minecraft.server.NetLoginHandler.b(NetLoginHandler.java:129)
    at net.minecraft.server.NetLoginHandler.a(NetLoginHandler.java:41)
    at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:61)
    at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:551)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:449)
    at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: java.lang.NullPointerException
    at java.lang.String.replace(Unknown Source)
    at net.blockheaven.kaipr.healthbarplus.HealthBarPlus.updateTitle(HealthBarPlus.java:124)
    at net.blockheaven.kaipr.healthbarplus.HealthBarPlus.updateTitle(HealthBarPlus.java:93)
    at net.blockheaven.kaipr.healthbarplus.HBPListener.onPlayerJoin(HBPListener.java:22)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301)
    ... 9 more