如何防止facebook打开图形api在没有图像时检索页面徽标

I got a carousel which shows facebook posts, I used a mask to make them all the same size, but this style is broken by a very small logo that returns multiple times. When I open the facebook post I see there is no image at all.

Example of a post (the images you see are not posted on facebook but probably a summary of images from the companies website):

enter image description here

The parameter full_image contains:

enter image description here

Why is that? And how can I make sure the parameter is actually empty when there is no image present.