Error

[19:32:45 ERROR]: Could not pass event PlayerJoinEvent to Yok-Kingdom v1.0
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:310) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerList.onPlayerJoin(PlayerList.java:298) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerList.a(PlayerList.java:157) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.LoginListener.b(LoginListener.java:144) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.LoginListener.c(LoginListener.java:54) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.NetworkManager.a(NetworkManager.java:231) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.ServerConnection.c(ServerConnection.java:148) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:814) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot.jar:git-Spigot-db6de12-18fbb24]
        at java.base/java.lang.Thread.run(Unknown Source) [?:?]
Caused by: java.lang.NullPointerException
        at java.base/java.util.regex.Matcher.appendExpandedReplacement(Unknown Source) ~[?:?]
        at java.base/java.util.regex.Matcher.appendReplacement(Unknown Source) ~[?:?]
        at java.base/java.util.regex.Matcher.replaceAll(Unknown Source) ~[?:?]
        at java.base/java.lang.String.replaceAll(Unknown Source) ~[?:?]
        at me.iclicks.yok.kingdom.events.Join.join(Join.java:87) ~[?:?]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:?]
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:?]
        at java.base/java.lang.reflect.Method.invoke(Unknown Source) ~[?:?]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
        ... 14 more