#vulnerable code 
                             private String rewardItem(Player player, ItemStack item) {
		if (player.getInventory().firstEmpty() != -1) {
			player.getInventory().addItem(item);
		} else {
			player.getWorld().dropItem(player.getLocation(), item);
		}

		String name = item.getItemMeta().getDisplayName();
		if (name == null || name.isEmpty()) {
			name = rewardParser.getItemName(item);
		}

		return langItemRewardReceived + name;
	} 
                            #location 8 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             private String rewardItem(Player player, ItemStack item) {
		if (player.getInventory().firstEmpty() != -1) {
			player.getInventory().addItem(item);
		} else {
			player.getWorld().dropItem(player.getLocation(), item);
		}
		ItemMeta itemMeta = item.getItemMeta();
		String name = itemMeta.hasDisplayName() ? itemMeta.getDisplayName() : rewardParser.getItemName(item);
		return StringUtils.replaceEach(langItemRewardReceived, new String[] { "AMOUNT", "ITEM" },
				new String[] { Integer.toString(item.getAmount()), name });
	}