Actually, nothing to do with it. What that change is doing is blocking any image as an example being loaded via http if you're on https
The issue is that its a browser enforced security system where an iframe cannot be displayed if the frame is HTTP and the main page is HTTPS, and has been in place for years. There is no way around that* short of
or disabling SSL on your server.
* There is one way around it that I experimented with, which is where I run a script to download the appropriate http page, and then display that within the iframe via https. But, any auxiliary support files referenced within (eg the CSS) don't get loaded, which means that in the end the success rate doing this and having it actually look right is so close to zero percent that it might as well be.