Doesn't fall back to a default sku when attempting to switch to an attribute adjustment that doesn't exist.

Here's my example.

You have a product with colors black and silver.

Black has sizes from small -> 4x
Silver has sizes from small -> 3x

Go to the product and select black / 4x.

Next change the color to silver.

The combo with fall back to silver / small which is good, but the sku goes to whatever may have been put into silver / 4x.

http://www.pinkgorillacycles.com/apparel/jackets/fieldsheer-slip-jacket

Thanks!