fix(wm): add bounds checking in move cmd

This commit ensures that when there is only one container on the target
workspace in a cross-monitor move, meaning that there won't be one
swapped back, we only decrement the focused container index on the
origin workspace if there is a focused container at an index greater
than 0.

fix #209

komorebi/src/window_manager.rs

@@ -1047,10 +1047,12 @@ impl WindowManager {
                         let origin_workspace =
                             self.focused_workspace_for_monitor_idx_mut(origin_monitor_idx)?;
 
+                        if origin_workspace.focused_container_idx() != 0 {
                             origin_workspace
                                 .focus_container(origin_workspace.focused_container_idx() - 1);
                         }
                     }
+                }
 
                 // if our MoveBehaviour is Swap, let's try to send back the window container
                 // whose position which just took over