List Builder popup shifts page to the right

I’m not sure if this is a general thing or something specific to my setup, but I’ve created a List Builder popup on my site blog.ridwan.me.

Whenever there’s a popup it shift my page slightly to the right, and when you close the popup is shifts back to its original spot. Just looks a little unprofessional.

Any fixes/suggestions?

https://www.ads-software.com/plugins/sumome/