Mixed content error

Hi, I have just installed the Newspaper theme and are currently working on the set-up in a staging enviroment. I have enabled SSL, but there is a strange mixed content error message that is giving me some trouble.

In source code under:
<!– Header style compiled by theme –>

There is a code section that looks like this:
.td-menu-background,
.td-search-background {
background-image: url(‘http://153449-www.web.tornado-node.net/wp-content/uploads/2017/09/10.jpg&#8217;);
}

So obvious this is the cause of the mixed content error, but I cant really find the settings that apply for this specific code. I have tried almost every setting and combinations of settings in the theme admin section with no luck.

I need some advice on this matter.

/ Daniel