Having trouble with CSS rule

[MoltenMonster]

I want to cycle between ; and !important; in CSS files, but when I try it, it shows a blank black line / bar at the bottom that immediately goes away (maybe its an error, the behavior might be due to something in my config?). How can I get any error messages for this?

local augend = require("dial.augend")
require("dial.config").augends:on_filetype({
	css = { augend.constant.new({ elements = { ";", "!important;" }, word = true, cyclic = true }) },
})