### 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.
ERR_FAIL_COND(!p_dock);
	Size2 borders = Size2(4, 4) * EDSCALE;
	
	Size2 dock_size = p_dock->get_size() + borders * 2;
	Point2 dock_screen_pos = p_dock->get_screen_position();
	int dock_index = p_dock->get_index() - 1;
	dock_slot[p_slot_index]->remove_child(p_dock);
	WindowWrapper *wrapper = memnew(WindowWrapper);
	wrapper->set_window_title(vformat(TTR("%s - Godot Engine"), p_dock->get_name()));
	wrapper->set_margins_enabled(true);
	gui_base->add_child(wrapper);
	wrapper->set_wrapped_control(p_dock);
	wrapper->set_meta("dock_slot", p_slot_index);
	wrapper->set_meta("dock_index", dock_index);
	wrapper->set_meta("dock_name", p_dock->get_name().operator String());
	wrapper->connect("window_close_requested", callable_mp(this, &EditorNode::_dock_floating_close_request).bind(wrapper));
	dock_select_popup->hide();
	if (p_show_window) {
		wrapper->restore_window(Rect2i(dock_screen_pos, dock_size), get_window()->get_current_screen());
	}
	_update_dock_containers();
	floating_docks.push_back(wrapper);
	_edit_current();
}
void EditorNode::_update_dock_containers() {