I had also faced similar error recently. While researching a fix on it I came across below given two solutions.
The first solution is if you are using Windows then you need to go to your files of the project as for e.g. a folder called ProjectSettings and then try to check inside your security properties files as for e.g. file with name ProjectVersion.txt or any other file which is from the assets folder. And now please confirm if your user has the read and write permissions. If you do not have those permissions then in the inside of properties in a tab called security you need to simply "edit" your settings to get write or total control.
The second solution is go to Edit -> Preferences -> click on DISABLE Show Asset Store Search Hits
After that you just need to close Unity and also if any text editors you have opened for using with the unity. And just open them again.
Now the annoying error must be fixed.