Remove product from cart if option unavailable

Prevents cases where a customer can order a product without options from
a saved cart.  This functionality existed in 1.4.9.6 but was never
ported to 1.5.x.

http://forum.opencart.com/viewtopic.php?f=20&t=85193
http://forum.opencart.com/viewtopic.php?f=161&t=28937#p144008