Only traverse child nodes if there are child nodes

Sometimes batman would try to traverse a nodes childNodes, but sometimes node.childNodes is null.

This is the error we would receive

![screen shot 2013-09-04 at 4 51 35 pm](https://f.cloud.github.com/assets/318823/1084965/2e35e874-15bd-11e3-8035-e098523be500.png)

A check fixes this.