Invisible quantity when 1

Here is what I have

Code:

                                            if(b.getType() == Material.GLOWSTONE)
                                            {
                                                Random rand = new Random();
                                               
                                                int amount = rand.nextInt(4);
                                               
                                                ItemStack one = new ItemStack(Material.GLOWSTONE_DUST);
                                               
                                                b.setType(Material.AIR);
                                               
                                                int a = one.getAmount();
                                                p.getInventory().remove(one);
                                                ItemStack two = new ItemStack(Material.GLOWSTONE_DUST, a + amount);
                                                p.getInventory().addItem(two);
                                                p.updateInventory();
                                            }

This seems to be working fine but when the random integer chooses 1 a new ItemStack in my inventory appears that seems to be invisible. When I click or drop it it disappears. How would I fix this or make it so the lowest random is 2 instead?

 

It's far more likely that the ItemStack is rendered invisible when the random value produced is zero. How to counter-act this issue? Simply add 1 to amount.