Blender Git Loki

Fix crash when deleting workspaces too fast

Delete workspaces via the menu was not refreshing the workspace tabs
drawing. This way if you deleted the non-active workspace with the "e" shortcut
from the workspace tab context menu and clicked on the workspace tabs again, it
would crash.

A few notes:
* Deleting a non-active workspace is changing which workspace is then active,
which is really strange.

* Even when deleting the active workspace which workspace then becomes active
seems random.

* Using notifiers (ND_WORKSPACE_DELETE) to delete the workspace seems rather
abusing notifiers in my humble opinion.

This is not an important bugfix anyways, people probably would rarely
run into this. I just ran into it while investigating another bug.