Using empty folder can lead to broken URLs. 

If an empty asset-merger.folder is specified (we put the rendered script and style directories into the root directory), Kohana_Assets::web_path returns a path with a leading slash.

This path is passed to Html::script and Html::style, which combines it with the path in Url::base (which returns a trailing slash), which results in doubles slashes in the URL. In some cases this has caused an issue.

I've used ltrim to remote the leading slash.