NullReferenceException caused by Unity's UIElementsEditorUtility.cctor

I keep getting an error and when I clear the console it shows up again, what does it mean, and how do I fix it?

Is play mode on when this error appears? If so, it means a script on one of your game objects need information that has not been given to it and because no information is available the script can not run. This typically will cause a program or game to crash. Unity is showing you this error to help you prevent this in your build version of the game.

Single clicking the error msg then checking the Hierarchy will show you which gameObject is affected.
Doubling clicking the error will open the script that is affected by the error in your chosen IDE.

Hope that helps.