### 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.
if (waiting_for_first_scan) {
		return; 
	}
	Ref<ConfigFile> config;
	config.instantiate();
	
	config->load(EditorPaths::get_singleton()->get_project_settings_dir().path_join("editor_layout.cfg"));
	_save_docks_to_config(config, "docks");
	_save_open_scenes_to_config(config);
	_save_central_editor_layout_to_config(config);
	editor_data.get_plugin_window_layout(config);
	config->save(EditorPaths::get_singleton()->get_project_settings_dir().path_join("editor_layout.cfg"));
}
void EditorNode::_save_docks_to_config(Ref<ConfigFile> p_layout, const String &p_section) {
	for (int i = 0; i < DOCK_SLOT_MAX; i++) {
		String names;
		for (int j = 0; j < dock_slot[i]->get_tab_count(); j++) {
			String name = dock_slot[i]->get_tab_control(j)->get_name();
			if (!names.is_empty()) {
				names += ",";
			}
			names += name;
		}
		String config_key = "dock_" + itos(i + 1);
		if (p_layout->has_section_key(p_section, config_key)) {
			p_layout->erase_section_key(p_section, config_key);
		}
		if (!names.is_empty()) {