I don’t need any of the “Main bar modules” for one of my products. When I blank them out I get a null dialog box that pops up when I first go into the product. You can check the null dialog at http://ourstagingarea.com/basic-growler. I only have one product in it and you can login as an admin with firstname.lastname@example.org and 12345678 as the credentials.
By design, you can not remove all main bar modules. But.. My suggestion, leave just images and text. Below you will find setting Kind of media types the users can add, and disable all. This way it will be display but without option to add. And no error will be call.