In Educon template When in "Feature Box" in "Button Link" i put the i.e. https://www.google.com the site crash and I have: 0 Object of class stdClass could not be converted to string how to put link to website in this place?

I went back to the backup page, and again after a few changes (other changes) I have "0 Object of class stdClass could not be converted to string ". What causes this error and how do I fix it?