Error handling interpolated if call

[ArmorDarks]

Hi

First of all, thanks for great project!

There seems to be an issue with evolution of inline if statement.

Example:

@mixin ekzo-font($version: 1123) {

    @font-face {

        src: url(test.eot#{if($version, '?#{$version}', '')});

    }

}

In Sass produces expected output, but libsass (used via node-sass) trows following error:

>> error reading values after test

Error can be workarounded by using quotes, though:

@mixin ekzo-font($version: 1123) {

    @font-face {

        src: url('test.eot#{if($version, '?#{$version}', '')}');

    }

}

[mgreter]

Minimal test case:

test {
  src: url(test.eot#{if(true, '?#{42}', '')});
}

expected:

test {
  src: url(test.eot?42); }