The latest change fixes the initial problem but introduces a new one!

The new issue is that doesn't matter what I check or uncheck on the Interface Preferences the only thing that is shown is the Editor in the SplitView.  It's reproducable every time, no matter what.  All you need to do is check every option, so that only the browser will be shown, then uncheck random options.

On another note, but still related, when the Editor is shown (after being hidden by the preferences) it doesn't preserve it's previous size.

I pushed enter by mistake, I'll explain here and someone can change the title to better describe the issue.

Under ProjectCenter's Interface Preferences, if any of the "Tear-Off Windows" are checked or unchecked, the "Project Builder" window pops up.  This is only reproducible if a project is open and the "Project Builder" window has been opened and closed at least once.

Best way to reproduce this is doing the following:
- Open a project
- Open "Project Builder"
- Close "Project Builder"
- Go into Interface Preferences
- Check, or uncheck, any option