I was doing this:

```
@line_items = LineItems.find_all_by_invoice_id(params[:id])
@payments = Payments.find_all_by_invoice_id(params[:id])
@total = @line_items.sum{ |item| item.cost }
@payment_total = @payments.sum{ |payment| payment.value }
@balance = @total - @payment_total
```

But when no payments had been made it was coming up with an error when

trying to sum nil, so I did this:

```
begin
@payment_total = @payments.sum{ |payment| payment.value }
rescue
@payment_total = 0
end
```

So, when the sum failed it returned @payment_total as zero. Now, SURELY,

there’s a better way to do this? I’m sure it’s obvious when you know

how. Please, enlighten me.