Gui crash

[calclavia]

This code will crash with this error when the inventory is commented out (like here): http://pastebin.com/U0eSd8kG. When the inventory is added things don't crash, but the GUI is broken (no background, button is invisible?).

public class MyGui extends Gui
{
    public MyGui()
    {
        super("myGui");

        add(new Button("button", "clickMe!")).onEvent((event, component) -> {
            System.out.println("Clicked!");
        }, ComponentEvent.ActionEvent.class, NetworkTarget.Side.BOTH);

        //add(new PlayerInventory("pInventory"));
    }
}