When I have an offside slideout open on the screen, I get the following Chrome console error:
Uncaught TypeError: Cannot read property ‘firstChild’ of null
at Object.afterOpen (offside.min.js?ver=1.7.2:1)
at v (offside.min.js?ver=1.7.2:1)
at g (offside.min.js?ver=1.7.2:1)
at HTMLLIElement.p (offside.min.js?ver=1.7.2:1)
Please note that I am using a local NGINX environment prior to deployment.
I am currently using the slideout as a widget panel (FacetWP filter shortcodes in a Text widget) for specific pages. The error occurs on both populated and unpopulated slideouts. I am also using Custom Sidebars.
To fix it right now, open wp-content/plugins/gp-premium/menu-plus/js/offside.min.js and replace the contents of it with this: https://pastebin.com/ENzMz6ub