Fix the following sort of crash, reported on the list. This is also

Fix the following sort of crash, reported on the list. This is also
#6884.

1. Open LyX. File>New. Document>Outline, to make sure the TOC is open.
That isn't necessary, but it helps you to see what is happening.
2. Create a section heading (alt-P, 2) with an x in it.
3. Split the screen.
4. File>New. You should now still see the TOC for the OLD buffer.
5. Click in the top screen. You now see an empty TOC (the one for the
empty buffer).
6. Click in the empty buffer. Other TOC!
7. Back to the "x" buffer. Empty TOC. Type something. Boom!

The problem is that teh setCurrentWorkArea() call eventually gets us to
structureChanged(), which accesses documentBufferView(). But that
doesn't get reset until later, and hence everything is out of sync.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@35999 a592a061-630c-0410-9148-cb99ea01b6c8