### 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
}
				DisplayServer::get_singleton()->window_request_attention();
				break;
			}
			_save_external_resources();
			_discard_changes();
		} break;
		case SETTINGS_UPDATE_CONTINUOUSLY: {
			EditorSettings::get_singleton()->set("interface/editor/update_continuously", true);
			_update_update_spinner();
			show_accept(TTR("This option is deprecated. Situations where refresh must be forced are now considered a bug. Please report."), TTR("OK"));
		} break;
		case SETTINGS_UPDATE_WHEN_CHANGED: {
			EditorSettings::get_singleton()->set("interface/editor/update_continuously", false);
			_update_update_spinner();
		} break;
		case SETTINGS_UPDATE_SPINNER_HIDE: {
			EditorSettings::get_singleton()->set("interface/editor/show_update_spinner", false);
			_update_update_spinner();
		} break;
		case SETTINGS_PREFERENCES: {
			editor_settings_dialog->popup_edit_settings();
		} break;
		case SETTINGS_EDITOR_DATA_FOLDER: {
			OS::get_singleton()->shell_show_in_file_manager(EditorPaths::get_singleton()->get_data_dir(), true);
		} break;
		case SETTINGS_EDITOR_CONFIG_FOLDER: {
			OS::get_singleton()->shell_show_in_file_manager(EditorPaths::get_singleton()->get_config_dir(), true);
		} break;
		case SETTINGS_MANAGE_EXPORT_TEMPLATES: {