"List index is 2 but list is only 1 item long for nth'" in intersect-browser-ranges()`

[mirisuzanne]

To reproduce:

// An actual use-case that demonstrates the problem
.use-case {
  @include with-browser-ranges(css-mediaqueries) {
    @include background-image(linear-gradient(red, blue));
  }
}

// A simplification of the issue
$ranges: (ie: "9" "11");
$new-ranges: (ie: "9");
@debug intersect-browser-ranges($ranges, $new-ranges);

At some point in the use-case, (ie: "9", opera: "9.5-9.6") is passed into intersect-browser-ranges() for the $new-ranges argument. The error comes from the single version number. Is that a mistake, or an edge-case that intersect-browser-ranges should support?

If the latter, I can submit a patch:

// support.scss line 280
// we may need to to the same for line 278 ($old-max)?
$new-max: if(length($new-range) > 1, nth($new-range, 2), $new-min);

This is the cause of oddbird/susy#395