### Godot version

4.1 rc3

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

This™
![image](https://github.com/godotengine/godot/assets/2223172/cb33110f-a5b0-400a-951f-3fa425f05714)

It can still happen, but it's more difficult to trigger.

### Steps to reproduce

1. Create a new scene with a Control node
2. Add Theme to the Control
3. Open Theme Editor
4. Clear the `theme` property in Control
5. Save, with Theme Editor opened
6. Restart

### Minimal reproduction project

N/A
editor_layout_save_delay_timer->start();
}
void EditorNode::_dock_split_dragged(int ofs) {
	editor_layout_save_delay_timer->start();
}
void EditorNode::_load_editor_layout() {
	Ref<ConfigFile> config;
	config.instantiate();
	Error err = config->load(EditorPaths::get_singleton()->get_project_settings_dir().path_join("editor_layout.cfg"));
	if (err != OK) { 
		
		TreeItem *root = FileSystemDock::get_singleton()->get_tree_control()->get_item_with_metadata("res:", 0);
		if (root) {
			root->set_collapsed(false);
		}
		if (overridden_default_layout >= 0) {
			_layout_menu_option(overridden_default_layout);
		}
		return;
	}
	_load_docks_from_config(config, "docks");
	_load_open_scenes_from_config(config);
	_load_central_editor_layout_from_config(config);
	editor_data.set_plugin_window_layout(config);
}
void EditorNode::_update_dock_slots_visibility(bool p_keep_selected_tabs) {