### 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
String action = undo_redo->get_current_action_name();
					if (action.is_empty()) {
						break;
					}
					switch (undo_redo->get_current_action_history_id()) {
						case EditorUndoRedoManager::GLOBAL_HISTORY:
							log->add_message(vformat(TTR("Global Redo: %s"), action), EditorLog::MSG_TYPE_EDITOR);
							break;
						case EditorUndoRedoManager::REMOTE_HISTORY:
							log->add_message(vformat(TTR("Remote Redo: %s"), action), EditorLog::MSG_TYPE_EDITOR);
							break;
						default:
							log->add_message(vformat(TTR("Scene Redo: %s"), action), EditorLog::MSG_TYPE_EDITOR);
					}
				}
			}
		} break;
		case EDIT_RELOAD_SAVED_SCENE: {
			Node *scene = get_edited_scene();
			if (!scene) {
				break;
			}
			String filename = scene->get_scene_file_path();
			if (filename.is_empty()) {
				show_warning(TTR("Can't reload a scene that was never saved."));
				break;
			}
			if (unsaved_cache && !p_confirmed) {
				confirmation->set_ok_button_text(TTR("Reload Saved Scene"));
				confirmation->set_text(