error message – please help – premium version error

I’ve been using the free version forever. I finally got the premium, then I got a fatal error, now upon activating, I get this error – The plugin generated 160 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

https://www.ads-software.com/plugins/yellow-pencil-visual-theme-customizer/