### 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
case SETTINGS_LAYOUT_DELETE: {
			current_menu_option = p_id;
			layout_dialog->set_title(TTR("Delete Layout"));
			layout_dialog->set_ok_button_text(TTR("Delete"));
			layout_dialog->set_name_line_enabled(false);
			layout_dialog->popup_centered();
		} break;
		case SETTINGS_LAYOUT_DEFAULT: {
			_load_docks_from_config(default_layout, "docks");
			_save_editor_layout();
		} break;
		default: {
			Ref<ConfigFile> config;
			config.instantiate();
			Error err = config->load(EditorSettings::get_singleton()->get_editor_layouts_config());
			if (err != OK) {
				return; 
			}
			_load_docks_from_config(config, editor_layouts->get_item_text(p_id));
			_save_editor_layout();
		}
	}
}
void EditorNode::_scene_tab_script_edited(int p_tab) {
	Ref<Script> scr = editor_data.get_scene_root_script(p_tab);
	if (scr.is_valid()) {
		InspectorDock::get_singleton()->edit_resource(scr);
	}
}
void EditorNode::_proceed_closing_scene_tabs() {