Bug 458

Steps to Reproduce:

1. Give the item of size 10 along with the arrival and the departure dates.
2. Give the slot size of 0.

Throwing an exception i.e Array Index Out of Bounds for findOnePerfectFit in the optimize method! 

Also need to throw an exception stating the slot size 0 is not valid.

Given test case:

@Test
	void testOptimize7() {
		Item is = new Item(5, new Day("13-Oct-2020"),new Day("20-Oct-2020"));
		Slot ss = new Slot(5);
		ArrayList<Item> itemArray = new ArrayList<Item>();
		itemArray.add(is);
		Optimize opt = new Optimize();
	    opt.findOnePerfectFit(itemArray, ss);
	    assertEquals(true, opt.getFound());
	}