If you install this module because you want pop-up warnings, but no icons, it appears to break the module. A note to the user might help.
This is a slightly unusual use case for this module, but:
I actually installed it on a site where I wanted the pop-up warnings, but no icons.
It wasn't immediately obvious to me that, if I deselected both "Add icon" checkboxes, the module basically stops working.
Once I realized that, it was pretty easy to activate "Add icon to external links" and then override the CSS to remove the icon.
Would it be possible to add a note to the Configuration page letting users know that you have to add the icon in order to get the pop-up warnings to work?