### 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 (!bool(EDITOR_GET("interface/scene_tabs/restore_scenes_on_load"))) {
		return false;
	}
	Ref<ConfigFile> config;
	config.instantiate();
	Error err = config->load(EditorPaths::get_singleton()->get_project_settings_dir().path_join("editor_layout.cfg"));
	if (err != OK) {
		return false;
	}
	if (!config->has_section(EDITOR_NODE_CONFIG_SECTION) || !config->has_section_key(EDITOR_NODE_CONFIG_SECTION, "open_scenes")) {
		return false;
	}
	Array scenes = config->get_value(EDITOR_NODE_CONFIG_SECTION, "open_scenes");
	return !scenes.is_empty();
}
bool EditorNode::ensure_main_scene(bool p_from_native) {