You can’t get a file through an insecure connection (http) from a html page served through a secure connection (https). If you’re going to use https (and you SHOULD!) then you need to get the script through a secure connection. To get the file, you should use:
And make sure that the file is being served through https, by configuring the server accordingly. Here’s a simple configuration for lighttpd, and here’s one for apache. If you don’t have a CA signed certificate, you could get one with letsencrypt ( www.letsencrypt.org/getting-started/ ). If you don’t control the server, you should get in contact with the person who does.