CSS minifier fails to parse nested @starting-style CSS at-rule

[AderitoSilva]

The CSS minifier treats nested @starting-style CSS at-rules as invalid CSS, and thus fails to minify CSS files that contain such rules.

An example case would be the following:

.my-active-class {
    color: red;
    @starting-style {
        color: green;
    }
}

The @starting-style CSS at-rule is still experimental, but using it in its nested form breaks parsing for the whole file.