Issue generating source maps

[ghost]

If I leave sourceMaps enabled in lessOptions, I end up with an error like this:

Invalid mapping: {"generated":{"line":4391,"column":2},"source":"../bittitan-css/lib/bootstrap/3.3.5/type.less","original":{"line":1,"column":null},"name":null}

When I narrow down the issue, it seems that it breaks when I have a media query nested inside a selector. Example:

.my-selector {
    @media (max-width: @screen-sm) {
        // styles
    }
}

So, I could either refactor any instances of nested media queries or set sourceMap to equal false.

[knownasilya]

Duplicate of #50