HOTFIX: Custom Layout Loads Properly In Postback

The custom layout placeholders for the Product Display and Product Review Listing widgets were only being registered when we were not in a postback, which caused custom layout to not load properly when in a postback.

The main place this was visible was on the Product Details page when the “after adding to cart” action was to stay on the product page. It would cause a postback which then changed the layout of the individual items inside these two widgets.