@gabelivan thank you a lot for your help.
Once I re-installed and configured the plugin again, everything worked fine. I had to reset everything first, because the first time I tried without resetting everything [just re-uploading the plugin] for some reason they where things missing, like for example the settings panel under each page or post… etc.
But now everything works fine.
I found this error just 24 or 48 hours ago, and I wasn’t using SG Optimizer when I installed Asset Cleanup, I removed it just before of that. But just to be sure, I went to my Cpanel and also deactivate their cache settings for this site there, because that plugin cache settings are inside Cpanel [Static, Dynamic, Mem].
I am also not using Asset Cleanup to minify js or css. I am using cloudflare for that, to compress all css and JS, cache everything and serve it through their CDN.
I am testing Asset Cleanup to remove all unnecessary scrips sitewide, and from particular posts and pages.
So far, everything works fine.
Thank you again @gabelivan
