Bug Report for V3

Steps to reproduce:

1. Give an item of value -1 along with arrival and departure date
2. Give the slot of value -1.

Should actually throw an exception like wrong input given but eclipse is showing that test case to be true.

The test case is:

	@Test
	void testOptimize4() {
		Item is = new Item(-1, new Day("13-Oct-2020"),new Day("20-Oct-2020"));
		Slot ss = new Slot(-1);
		ArrayList<Item> itemArray = new ArrayList<Item>();
		itemArray.add(is);
		Optimize opt = new Optimize();
	    opt.findOnePerfectFit(itemArray, ss);
	    assertEquals(false, opt.getFound());
	}