### 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.
}
			img->convert(Image::FORMAT_RGB8);
			
			String temp_path = EditorPaths::get_singleton()->get_cache_dir();
			String cache_base = ProjectSettings::get_singleton()->globalize_path(p_file).md5_text();
			cache_base = temp_path.path_join("resthumb-" + cache_base);
			
			post_process_preview(img);
			img->save_png(cache_base + ".png");
		}
	}
	save.step(TTR("Saving Scene"), 4);
	_save_scene(p_file, p_idx);
	if (!singleton->cmdline_export_mode) {
		EditorResourcePreview::get_singleton()->check_for_invalidation(p_file);
	}
}
bool EditorNode::_validate_scene_recursive(const String &p_filename, Node *p_node) {
	for (int i = 0; i < p_node->get_child_count(); i++) {
		Node *child = p_node->get_child(i);
		if (child->get_scene_file_path() == p_filename) {
			return true;
		}
		if (_validate_scene_recursive(p_filename, child)) {
			return true;
		}
	}
	return false;
}
int EditorNode::_save_external_resources() {