Clicking an item in the panel frame wasn't working when inside an <iframe>

This little fix makes the panel work when inside an `<iframe>`.

This is useful, for example, when you're using Sami with Jenkins+[HTML Publisher Plugin](https://wiki.jenkins-ci.org/display/JENKINS/HTML+Publisher+Plugin) to build your docs, since the plugin uses an `<iframe>` to embed the webpage you specify.