The dialog triggered by the filemanager is misplaced with a broken header

The confirm dialog triggered by the filemanager is positioned at the top left corner of the screen, with broken header structure. This seems to be a regression caused by some changes introduced in MDL-33671

Steps to reproduce:

1. Login as Admin.
2. Go to "Private files"
3. Create a folder ("New Folder") in the private files area
4. After you have created the folder, edit the same folder
5. Change the folder's name ("New Folder 1") and press "Update"

Expected: The confirmation dialog is placed in the center of the screen without any styling issues.

Result: The confirmation dialog is placed in the top left corner of the screen with some header styling issues.