[tbworld]

Not that I completely understood your question. I needed to see a picture of your style manager, but if your style is the master style then the steps below will fix your problem.

1.) Backup Site.
2.) Download the style (Export it to save it).
3.) Upload 'Tools.php' and create new master style.
4.) Create new parent style from vbulletin's master style.
5.) Upload (import) your saved style and attach it as a child to the new parent you created (not as a child of your master style).

Now you can delete a temporary style without that error.

There are brighter minds out there, maybe they know a simpler solution.