Prevent inserting undefined values

The following SQL query was executed:

INSERT INTO `cv` (`first_name`, `last_name`, `father_name`, `city`, `district`, `transfer`, `nationality`, `email`, `icq`, `skype`, `birth_date`, `marital_status`, `gender`, `children_status`, `id`) VALUES ('asdsd', , , '', '', , , 'i@marat.by', , , , , , , 2) ON DUPLICATE KEY UPDATE `first_name` = 'asdsd', `last_name` = undefined, `father_name` = undefined, `city` = '', `district` = '', `transfer` = undefined, `nationality` = undefined, `email` = 'i@marat.by', `icq` = undefined, `skype` = undefined, `birth_date` = undefined, `marital_status` = undefined, `gender` = undefined, `children_status` = undefined;
Merge pull request #19 from vectart/master

Prevent inserting undefined values