Solved Null MaterialData problem

Hey everyone, I have a weird problem that is giving me and NPE while trying to retrieve random items from a List<ItemStack>.

Code:java

    private void giveItems(Player p, String group){
        Random rnd = new Random();
        int i = rnd.nextInt(plugin.getItems(group).size());
        int amount = rnd.nextInt(64);
 
        p.sendMessage("i = " + i + " | amount = " + amount);
 
        MaterialData md = ItemManager.getItems().get(i); // This is null.
 
        p.sendMessage("" + md);
 
        ItemStack item = md.toItemStack(amount);
 
        p.sendMessage("itemStack : " + item);
 
        if(item != null){
            p.getInventory().addItem(item);
        }
        p.sendMessage("§7You got a §6" + item.getType() + "§7(§6" + amount + "§7)");
    }

Where 'MaterialData md = ItemManager.getItems().get(i);' is, it drags an NPE to the next line which is 'ItemStack item = md.toItemStack(amount);'
This is how it prints out the debugs


Stacktrace:

Code:

[SEVERE] Could not pass event PlayerInteractEvent to SignG v1.0
org.bukkit.event.EventException
 at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:427)
 at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
 at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
 at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
 at org.bukkit.craftbukkit.v1_6_R3.event.CraftEventFactory.callPlayerInteractEvent(CraftEventFactory.java:190)
 at net.minecraft.server.v1_6_R3.PlayerInteractManager.interact(PlayerInteractManager.java:373)
 at net.minecraft.server.v1_6_R3.PlayerConnection.a(PlayerConnection.java:630)
 at net.minecraft.server.v1_6_R3.Packet15Place.handle(SourceFile:58)
 at net.minecraft.server.v1_6_R3.NetworkManager.b(NetworkManager.java:296)
 at net.minecraft.server.v1_6_R3.PlayerConnection.e(PlayerConnection.java:116)
 at net.minecraft.server.v1_6_R3.ServerConnection.b(SourceFile:37)
 at net.minecraft.server.v1_6_R3.DedicatedServerConnection.b(SourceFile:30)
 at net.minecraft.server.v1_6_R3.MinecraftServer.t(MinecraftServer.java:592)
 at net.minecraft.server.v1_6_R3.DedicatedServer.t(DedicatedServer.java:227)
 at net.minecraft.server.v1_6_R3.MinecraftServer.s(MinecraftServer.java:488)
 at net.minecraft.server.v1_6_R3.MinecraftServer.run(MinecraftServer.java:421)
 at net.minecraft.server.v1_6_R3.ThreadServerApplication.run(SourceFile:583)
Caused by: java.lang.NullPointerException
 at me.kreashenz.signg.SignListener.giveItems(SignListener.java:59)
 at me.kreashenz.signg.SignListener.onPlayerInteract(SignListener.java:34)
 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:425)
 ... 16 more