Add to this, a concern I have about using session data to move around the cart is that the session data goes away when a logged in customer with items in the cart logs off (or gets logged off) and then sort of back at square one...

Now, I could force the text field to contain a single character if it was pushed as empty, but not exactly sure that's the route I would want to go, might need to look at how it is handled later, like when brought back to the product after clicking on the item in the cart, does it contain the new single character or is it removed?