Stop safari from blowing up

Fixes #138 and #173 

@zackbloom @TrevorBurnham @marcneuwirth 
This is true. :/ It accidentally works since it always returns -1 thus never tries to access those keys. 

The keys that are a issue are the ones that are undefined. (URL, etc) 
![screenshot 2014-11-03 15 22 57](https://cloud.githubusercontent.com/assets/4588318/4889624/90c82db6-6397-11e4-9bc3-43f9603d1ed8.png)

So I guess this puts the fix back on the drawing board. Though safari still seems to work with pace with this fix.