Unable to create multiple default Order Bys with CivicReport

The attached file "Bug.php" is a sample CiviReport template with six display columns, four of them are configured to be in the default "order by" list. When the template is opened, only the first default order by column shows up (see "Before.jpg").

I think I found the error in Form.php. I have attached an updated Form.php (see lines 538 through 551). "After.jpg" shows what the screen looks like when using the updated Form.php file: all four columns show up in the default order by list.