The problem is that the whatschat widget adds a 300px wide transparent iframe in the corner of the page. This iframe covers a portion of the Divi footer, blocking users from clicking on the links in that part of the footer (e.g. the social icons).
As far as I can tell, the widget never actually uses the full 300px area it allocates for itself. So to get the footer links working again, we can just decrease the size of the widget's iframe, using the following CSS:
Related Post: Adding CSS to the Divi Theme