Icon alias which does not have a content is rendered in the generated css

Consider an alias defined as:

.AFIndexedIcon:alias {
color: #167E01;
}

Clearly the alias does not represent an Icon, because it does not have a content. But skin framework does not enforce the IconStyle usage. Neither does skin framework render any of the aliases into the generated css.

The issue here is that Icon:aliases defined like this is getting rendered into the generated css.