Update Csv.php

[CarlosASLJR]

If the CSV field is empty it can cause an SQL error, replacing it with NULL does not cause an error.

Note: Database column cannot be "NOT NULL"

[ecourtial]

Hi @CarlosASLJR You can use our fork to check if you still have the issue :) https://github.com/wizaplace/php-etl Changelog here: https://github.com/wizaplace/php-etl/blob/master/changelog.MD :)