Script error for Single Listing Content Markup options

First thanks for this excellent plugin, I’m still playing around with it. However I got an error while customizing Listing Content Markup options, the Add Dynamic Fields button doesn’t work and thrown script error like:

favorites-admin.min.js?ver=2.2.0:1 Uncaught TypeError: Cannot read property 'execCommand' of null
    at ListingCustomizer.e.addFieldToEditor (favorites-admin.min.js?ver=2.2.0:1)
    at HTMLButtonElement.<anonymous> (favorites-admin.min.js?ver=2.2.0:1)
    at HTMLDocument.dispatch (load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils,jquery-ui-sortable,jquery-u&load[]=i-slider,jquery-touch-punch,iris,wp-color-picker,underscore,backbone,wp-util,wp-backbone,media-models,moxiejs,plupload,wp-pluplo&load[]=ad&ver=4.9.8:3)
    at HTMLDocument.r.handle (load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils,jquery-ui-sortable,jquery-u&load[]=i-slider,jquery-touch-punch,iris,wp-color-picker,underscore,backbone,wp-util,wp-backbone,media-models,moxiejs,plupload,wp-pluplo&load[]=ad&ver=4.9.8:3)

If you need any more info about this I can provide a temp login to our site. Thanks!