fix eventual bug

Hello!
I had some strange bug after connecting debug-toolbar:
 Fatal error: Call to a member function as_array() on a non-object in \debug-toolbar\classes\Kohana\Debugtoolbar.php on line 499
I noticed that it happened while trying to call as_array() for my APPATH/config/default.database.php file. It's just a clone of database.php, nothing unusual. So I added a simple check to debug-toolbar and now it works fine!
I think this fix may be helpful.