Thank you for using the Turn Off the Lights Firefox extension!
Sorry for the bad experience.
In the Turn Off the Lights options page there is an option to hide the page action icon in the address bar. It's years that the gray lamp icon is in the address bar such as in the Google Chrome and Opera web browser. It shows you the icon on the web pages where you can dims the page and not on the settings page from Firefox. Please submit this feedback also to the Firefox extension team. (You are just using the new WebExtensions technology)
