Having trouble with the Preset Pack User Guide PDF. Paypal won’t take $0 dollars as value. When I click on the shopping cart and then straight into “checkout with paypal” yellow icon I get the following error message:

• Notice: Undefined index: items in uc_cart_view_form_submit() (line 724 of/home/apertureexpert/sites/dev.apertureexpert.com/apertureexpert.com/sites/all/modules/ubercart/uc_cart/uc_cart.module).
• Warning: Invalid argument supplied for foreach() in uc_cart_view_form_submit() (line 724 of/home/apertureexpert/sites/dev.apertureexpert.com/apertureexpert.com/sites/all/modules/ubercart/uc_cart/uc_cart.module).
• PayPal reported an error: 10401: Order total is invalid