I'm trying to edit a page with Visual Composer, But the page keeps loading, The preloader keeps loading the plugin logo.
Here is a screenshot of the issue:

- WordPress version: 4.9.8
- Plugin version: 5.1.1
The console errors:
Uncaught TypeError: $(...).slick is not a function
at HTMLDocument.eval (eval at <anonymous> (load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:2), <anonymous>:3:65)
at i (load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:2)
at Object.add [as done] (load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:2)
at a.fn.init.n.fn.ready (load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:2)
at eval (eval at <anonymous> (load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:2), <anonymous>:2:18)
at eval (<anonymous>)
at load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:2
at Function.globalEval (load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:2)
at Ha (load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:3)
at a.fn.init.append (load-scripts.php?c=1&load[]=jquery-core,jquery-migrate,utils,moxiejs,plupload,jquery-ui-core,jquery-ui-widget&ver=4.9.8:3)
14 Mixed Content: The page at '<URL>' was loaded over HTTPS, but requested an insecure image '<URL>'. This content should also be served over HTTPS.
How to solve this issue?