When I add a product image and no images in the product gallery, the main product image shows on the front end product page, but when I add additional images in the gallery, the main product image vanishes and I have to add it to the product gallery as well as the main product image, why is that? why does the main product image vanish when I add images to the product gallery and the page shows the first image of the product gallery as the main image? shouldn’t it show both?