org.bukkit.command.CommandException: Unhandled exception executing command 'ping' in plugin FactionsEssentials v1.5.9
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[spigot.jar:git-Spigot-b78586d-f3356f1]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[spigot.jar:git-Spigot-b78586d-f3356f1]
        at org.bukkit.craftbukkit.v1_12_R1.CraftServer.dispatchCommand(CraftServer.java:644) ~[spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.PlayerConnection.handleCommand(PlayerConnection.java:1385) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1220) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:45) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:1) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.PlayerConnectionUtils$1.run(SourceFile:13) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_131]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_131]
        at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:46) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:747) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:405) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:678) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:576) [spigot.jar:git-Spigot-b78586d-f3356f1]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_131]
Caused by: java.lang.NoClassDefFoundError: org/bukkit/craftbukkit/v1_11_R1/entity/CraftPlayer
        at me.nikk.Fess.Ping.onCommand(Ping.java:25) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spigot.jar:git-Spigot-b78586d-f3356f1]
        ... 15 more
Caused by: java.lang.ClassNotFoundException: org.bukkit.craftbukkit.v1_11_R1.entity.CraftPlayer
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:91) ~[spigot.jar:git-Spigot-b78586d-f3356f1]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[spigot.jar:git-Spigot-b78586d-f3356f1]
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_131]
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_131]
        at me.nikk.Fess.Ping.onCommand(Ping.java:25) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spigot.jar:git-Spigot-b78586d-f3356f1]
        ... 15 more