output-layout: keep active workspace when destroying output

Currently, when destroying the current output, core focuses the
next output (if any) but does not switch to the same workspace
that the user was previously using. Switch to the same workspace
so the user can pick up where they left off.

src/core/output-layout.cpp

@@ -547,7 +547,13 @@ struct output_layout_output_t
 
         /* It doesn't make sense to transfer to another output if we're
          * going to shut down the compositor */
-        transfer_views(wo, shutdown ? nullptr : get_core().seat->get_active_output());
+        wf::output_t *new_output = shutdown ? nullptr : get_core().seat->get_active_output();
+        transfer_views(wo, new_output);
+        if (new_output &&
+            (wo->wset()->get_workspace_grid_size() == new_output->wset()->get_workspace_grid_size()))
+        {
+            new_output->wset()->set_workspace(wo->wset()->get_current_workspace());
+        }
 
         wf::output_removed_signal data2;
         data2.output = wo;