corrupted tab decorations after shutting down monitor

[andresilva]

After shutting down the monitor and then turning it back on, all workspaces will include tab decorations (assuming there was any tabbed group before shutting down the monitor). The decorations go away after switching to the workspace that does include a tabbed group.

How to reproduce:

1. Create a tabbed group on workspace 1
2. Open a window on workspace 2
3. Turn off/on monitor (assuming there is only monitor)
4. Workspace 2 with a single window should now have the same tab decorations as workspace 1