Hello Trexma, Tamam Alhamodlelah 🙂
Do you mean the black overlay that appears above the screen when you click “Insert Shelf” http://take.ms/flygK ? This seems to be a plugin issue not a theme issue. You can contact the plugin authors to fix this issue and let me know if you needed any help in that.
If you mean another issue please describe its steps cause I can’t find another issue.