Enter key (instead of mouse click) doubles 'Add to Cart' qty

[jasonhendee]

I have done some mods to the 'BuyProductDialog' control, so I'm curious if this is a bug I've introduced, or if it's something that anyone else can re-create.

Scenario:
- Version: 7.0.7.14481
- Only appears to happen in Google Chrome
- On a product display page, click the "Add to Cart" button; it adds whatever quantity you have in the Quantity textbox to your cart
- On that same page, put your cursor in the Quantity text box, and hit the enter key (as opposed to clicking the "Add to Cart" button); on my site, it doubles whatever value is in the Quantity textbox when added to the cart

In my testing, removing DefaultButton="AddToBasketButton" from the BuyProductPanel tag makes this problem go away.