Fixed error in IE that prevents logs from showing

IE doesn't clone completely empty text nodes on ```cloneNode(true)```, see http://jsfiddle.net/SFqk9 for an example.
This results in a null reference exception when setting ```span.lastChild.nodeValue``` in the ```renderSpan``` function. By putting a space char in the text node this doesn't happen as the node gets cloned correctly.

With this change, the logs show up correctly in IE:
![logs](https://f.cloud.github.com/assets/1376924/1910467/f9340166-7d17-11e3-8e70-9a006a338e99.png)