Thank you Design.
Before, I got a blanc page witj absolutely nothing.
Now I see my webshop-the specials page again, but WARNING: An Error occurred, please refresh the page and try again.

When looking in the logs it says:
[10-Apr-2015 10:41:34 Europe/Berlin] PHP Warning: mysqli_query(): Empty query in C:\xampp\htdocs\zencart\includes\classes\db\mysql\query_factory.php on line 43

[10-Apr-2015 10:41:34 Europe/Berlin] PHP Fatal error: 0: :: ==> (as called by) C:\xampp\htdocs\zencart\includes\modules\pages\specials\main_template_vars.php on line 29 <== in C:\xampp\htdocs\zencart\includes\classes\db\mysql\query_factory.php on line 155