Invoice node edit form needs to order line items by weight

In _invoice_get_invoice_items() in invoice.form.inc, the query in line 717 needs "ORDER BY created ASC, weight ASC" instead of just "ORDER BY created ASC". That's how it's done in invoice_load(). I had to make the change in my application because I'm creating invoices programmatically, and since 'created' is only granular to the second, it's the same for all my line items. Therefore, I depend on weight to order the items.