[21:17:54 WARN]: Unexpected exception while parsing console command "ref"
org.bukkit.command.CommandException: Unhandled exception executing command 'ref' in plugin ReferalSystem v1.0
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[spigot.jar:git-Spigot-21fe707-e1ebe52]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[spigot.jar:git-Spigot-21fe707-e1ebe52]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand(CraftServer.java:641) ~[spigot.jar:git-Spigot-21fe707-e1ebe52]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchServerCommand(CraftServer.java:627) [spigot.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.DedicatedServer.aO(DedicatedServer.java:412) [spigot.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:375) [spigot.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [spigot.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot.jar:git-Spigot-21fe707-e1ebe52]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_131]
Caused by: java.lang.ClassCastException: org.bukkit.craftbukkit.v1_8_R3.command.ColouredConsoleSender cannot be cast to org.bukkit.entity.Player
        at main.cmdsMain.onCommand(cmdsMain.java:14) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spigot.jar:git-Spigot-21fe707-e1ebe52]
        ... 8 more