### Godot version

4.1.beta (7b1387ff2)

### System information

Mageia 9, Linux

### Issue description

When opening an empty project in latest `master`, I get these errors:
```
ERROR: Index p_idx = -1 is out of bounds (edited_scene.size() = 1).
   at: get_scene_path (editor/scu/../editor_data.cpp:880)
ERROR: Index p_idx = -1 is out of bounds (edited_scene.size() = 1).
   at: check_and_update_scene (editor/scu/../editor_data.cpp:683)
ERROR: Index p_idx = -1 is out of bounds (edited_scene.size() = 1).
   at: set_edited_scene (editor/scu/../editor_data.cpp:745)
```

Possibly related to recent changes to restore past sessions, but there's nothing to restore in this case?

### Steps to reproduce

- Create a new project, edit it
- Quit to project manager
- Re-open the newly created project -> errors

### Minimal reproduction project

Empty project.
dock_select->queue_redraw();
			dock_select_rect_over_idx = nrect;
		}
		if (nrect == -1) {
			return;
		}
		Ref<InputEventMouseButton> mb = me;
		if (mb.is_valid() && mb->get_button_index() == MouseButton::LEFT && mb->is_pressed() && dock_popup_selected_idx != nrect) {
			Control *dock = dock_slot[dock_popup_selected_idx]->get_current_tab_control();
			if (dock) {
				dock_slot[dock_popup_selected_idx]->remove_child(dock);
			}
			if (dock_slot[dock_popup_selected_idx]->get_tab_count() == 0) {
				dock_slot[dock_popup_selected_idx]->hide();
			} else {
				dock_slot[dock_popup_selected_idx]->set_current_tab(0);
			}
			dock_slot[nrect]->add_child(dock);
			dock_popup_selected_idx = nrect;
			dock_slot[nrect]->set_current_tab(dock_slot[nrect]->get_tab_count() - 1);
			dock_slot[nrect]->set_tab_title(dock_slot[nrect]->get_tab_count() - 1, TTRGET(dock->get_name()));
			dock_slot[nrect]->show();
			dock_select->queue_redraw();
			_update_dock_containers();
			_edit_current();
			_save_editor_layout();
		}
	}
}
void EditorNode::_dock_popup_exit() {