Mixed content error

Hi there,

Since I updated all-in-one-event-calendar a couple of days ago to version 2.5.21 I get Mixed content error, which causes not to display the calendar anymore on my website.
My websites uses SSL for https connection.

I get the following errors in the element inspector:

Mixed Content: The page at ‘https://sitename.nl/cultuur/’ was loaded over HTTPS, but requested an insecure script ‘http://sitename.nl/wp-content/plugins/all-in-one-event-calendar/public/js/scripts/calendar.js?ver=2.5.21’. This request has been blocked; the content must be served over HTTPS.

and

Uncaught Error: Script error
http://requirejs.org/docs/errors.html#scripterror
at makeError (ai1ec_js_widget.js:15)
at HTMLScriptElement.onScriptError (ai1ec_js_widget.js:15)
at Function.req.load (ai1ec_js_widget.js:15)
at Object.load (ai1ec_js_widget.js:15)
at n.load (ai1ec_js_widget.js:15)
at n.fetch (ai1ec_js_widget.js:15)
at n.check (ai1ec_js_widget.js:15)
at n.enable (ai1ec_js_widget.js:15)
at Object.enable (ai1ec_js_widget.js:15)
at n.<anonymous> (ai1ec_js_widget.js:15)

Is there any fix for this?

Thanks in advance.