Fix attempted string cast of classes that cannot be cast to string

I had an issue where closures in my config files were being cast to string.

> [2013-09-30 11:28:41] log.ERROR: exception 'ErrorException' with message 'Object of class Closure could not be converted to string' in ...\app\storage\views\3ac278c0cf4e0defb1e30748a39554a8:14