[Vault API] Adding permission error

So I'm using this code:

Code:java

public boolean onCommand(CommandSender sender, Command cmd, String cmdLabel, String[] args) {
    Player p = (Player)sender;
    if (cmd.getName().equalsIgnoreCase("kitshop")) {
        if (args.length == 0) {
            p.sendMessage("§7Kit Shop(1/1) §a§oPvP");
          return true;
        }
        if ((args[0].equalsIgnoreCase("pvp"))) {
            if(p.hasPermission("kits.pvp")) {
                sender.sendMessage("§cYou already own this kit!");
            } else {
                Main.permission.playerAdd(p, "kits.pvp");
                sender.sendMessage("§7You have bought the §a§oPvP §7kit!");
            }
            return true;     
        }
    }
return true;
}
}

But when I actually do the command (/kitshop pvp) it gives me an internal error!

Stack trace:

Code:

[21:32:58 ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'kitshop' in plugin tKits v2.15.1
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:196) ~[craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at org.bukkit.craftbukkit.v1_7_R1.CraftServer.dispatchCommand(CraftServer.java:542) ~[craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.PlayerConnection.handleCommand(PlayerConnection.java:932) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.PlayerConnection.a(PlayerConnection.java:814) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.PacketPlayInChat.a(PacketPlayInChat.java:28) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.PacketPlayInChat.handle(PacketPlayInChat.java:47) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:146) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:655) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:250) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:545) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:457) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
Caused by: java.lang.NullPointerException
    at tKits.KitShop.CmdKitShop.onCommand(CmdKitShop.java:28) ~[?:?]
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[craftbukkit-1.7.2-R0.3-20131225.043511-4.jar:git-Bukkit-1.7.2-R0.2-3-g530fcb7-b2978jnks]
    ... 13 more

Line 28: Main.permission.playerAdd(p, "kits.pvp");

Thanks, any help appreciated.

 

CactusComboPvP Main.permission is not set (i.e. null). Also check if(sender instanceof Player) before casting to Player