craftyjs/Crafty — pull request #840 by fdavis (2014-12-05 06:02:57+00:00)
Title: report error if scene does not exist

The error for borking a scene name was a bit misleading. Its not that hard to correlate, but a more direct message should help people new to crafty like me, with our typos. :)
```
Uncaught TypeError: Cannot read property 'initialize' of undefined
```
error reproduced here: http://jsfiddle.net/z3bbzehv/