BUG: Removed the debug call to d($...) that was left in preheaders/checkout.php and would show up when checkout forms were submitted with empty fields. (Thanks, Nicolas)

git-svn-id: https://plugins.svn.wordpress.org/paid-memberships-pro/trunk@986458 b8457f37-d9ea-0310-8a92-e5e31aec5664