Gracefully handle deleted workspaces for users who had it as active

Here's a scenario involving user 1 and user 2:

1. User 1 creates Workspace A because it’s awesome
2. User 2 sets Workspace A as active to check-out this new awesome workspace
3. User 1 doesn't think her new Workspace A is so awesome any more
4. User 1 deletes Workspace A
5. User 2 now has a deleted workspace as her active workspace
6. User 2 is really sad because she now has a WSOD

Proposed solution:
Switch to the "live" workspace if the active workspace no longer exists