Error thrown on non-whitelisted object than can't be cast to string n…

…ow a SPL RuntimeException.

classes/security.php

@@ -175,7 +175,7 @@ public static function htmlentities($value)
 			// Throw exception when it wasn't whitelisted and can't be converted to String
 			if ( ! method_exists($value, '__toString'))
 			{
-				throw new \Fuel_Exception('Object class "'.get_class($value).'" could not be converted to string or '.
+				throw new \RuntimeException('Object class "'.get_class($value).'" could not be converted to string or '.
 					'sanitized as ArrayAcces. Whitelist it in security.whitelisted_classes in app/config/config.php '.
 					'to allow it to be passed unchecked.');
 			}