Odd - client settings are things like hotbar arrangments and changes to the GUI you make which are saved locally on your computer/PS4/PS5. Sounds like a glitch where a change wasn't saved properly. Try opening your hotbars and move an icon around or change it, then return it to how it was, and then see if it throws up the error again.

If it doesn't, it was probably just a momentary glitch that isn't really anything to worry about too much.