Radio button options displayed on the same row in Filepicker (Firefox)

Please test this in multiple browsers.

Test 

1. Log in as Admin.
2. Go to 'Private files'
3. Click on the "Add..." button, upload a file and save changes.
4. Create a Course and go to the Course.
5. Enable editing and open the activity chooser.
6. In the activity chooser, click on the 'File' resource.
7. In "Select files" click on the "Add.." button.
8. Select the 'Private files' repository and click on the previously uploaded file.
9. In the Select file dialog:
   • make sure the select options (radio buttons) are NOT displayed horizontally in the same row, but vertically one after another.