Knapsack has error


```
var uu = [
      new KnapsackItem({ value: 3, weight: 2 }),
      new KnapsackItem({ value: 4, weight: 3 }),
      new KnapsackItem({ value: 5, weight: 4 }),
      new KnapsackItem({ value: 7, weight: 5 }),
    ];
var b  = new Knapsack(uu, 7);
b.solveZeroOneKnapsackProblem()
```