Support

MagicEraser is meant to be used while on J3, before the update.

The problem here is that the extension files are removed. You only have a database record in the #__extensions table left behind. Unfortunately, Joomla does not give an option to remove these phantom records. While it says to remove "it" (meaning the extensions table record) manually, doing so would be a bad idea because it ties into the #__assets table. Removing the assets record will create a "hole" in that double linked list you cannot come back from and your site might develop strange issues in the future.

The best thing you can do is ignore this record.

If it bothers you so much, you can find and remove the corresponding extensions table record (check the ID next to the extension reported in Joomla's backend interface), knowing that there is a phantom, useless, but otherwise harmless entry in the #__assets table.

Finally, do keep in mind that if you do follow the migration instructions in the documentation you never end up in this situation. This has only happened because the files were removed manually, instead of uninstalling the extension after upgrading to Joomla! 4.

You're welcome and have a great day!