This appears because you have an active Skatter setup in your file. Go to Skatter’s Render List and delete everything.
If there is nothing, Skatter will stay silent.
That’s weird, I don’t have anything in the console when opening your file. There are no attributes that should trigger Skatter.
Are you starting Skatter manually?
To silence Skatter, edit C:\ProgramData\SketchUp\SketchUp 2018\SketchUp\Plugins\jbb_skatter\rb\methods.rb and set @debug = false on line 6
(Please don’t look at the code, it’s embarrassing )