Adding items using addItems method on SimpleGUI does not seem to work when creating a Tab GUI

[tank-o]

Version 0.10

I was creating a tab GUI and the example worked great, I then tried just adding specific items using the addItems method instead of using the fill method and it would not add any items.

I stepped into the method below and the emptyIndex was constantly coming back as -1, why it was doing that I am not sure, since the GUI had not had any items added to it yet.

    @Override
    public void addItems(@NotNull Item... items) {
        for (Item item : items) {
            int emptyIndex = ArrayUtils.findFirstEmptyIndex(items);
            if (emptyIndex == -1) break;
            setItem(emptyIndex, item);
        }
    }

This is the code to reproduce the GUI that isnt working, this exact code works perfectly fine with using fill or setItem

  GUI pickaxeTab = new SimpleGUI(9, 3);
  GUI axeTab = new SimpleGUI(9, 3);
  for (int i =0; i < 9; i++){
      pickaxeTab.addItems(new SimpleItem(new ItemBuilder(Material.IRON_PICKAXE)));
      axeTab.addItems(new SimpleItem(new ItemBuilder(Material.IRON_AXE)));
  }
  menu = new GUIBuilder<>(GUIType.TAB)
          .setStructure(
                  "# # # 0 # 1 # # #",
                  "x x x x x x x x x",
                  "x x x x x x x x x",
                  "x x x x x x x x x")
          .addIngredient('x', Markers.ITEM_LIST_SLOT_HORIZONTAL)
          .addIngredient('#', Border::new)
          .addIngredient('0', new PickTab(0))
          .addIngredient('1', new AxeTab(1))
          .setGUIs(Arrays.asList(pickaxeTab, axeTab))
          .build();
}

[D0gmaDev]

I believe that should fix it: #15