Could you provide more details please, maybe screenshots?
Also please note that I only tested this using NWjs, the result of this script may vary using other browsers.
EDIT: Never mind I know what you mean now, I thought there were problems with the script.
To be honest I have no clue how to prevent that icon from appearing, there might be a way to block the button itself.
I'll ask this question to some experienced JS devs, they might find an easy solution for you soon.
Thank you! I tried to take a screenshot but as i press any button the icon disappears. It's problematic not for the icon itself, but the fact it makes it difficult to properly use the middle mouse button.