### 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 FILE_CLOSE_OTHERS: {
			tab_closing_menu_option = -1;
			for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
				if (i == editor_data.get_edited_scene()) {
					continue;
				}
				tabs_to_close.push_back(editor_data.get_scene_path(i));
			}
			_proceed_closing_scene_tabs();
		} break;
		case FILE_CLOSE_RIGHT: {
			tab_closing_menu_option = -1;
			for (int i = editor_data.get_edited_scene() + 1; i < editor_data.get_edited_scene_count(); i++) {
				tabs_to_close.push_back(editor_data.get_scene_path(i));
			}
			_proceed_closing_scene_tabs();
		} break;
		case FILE_CLOSE_ALL: {
			tab_closing_menu_option = -1;
			for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
				tabs_to_close.push_back(editor_data.get_scene_path(i));
			}
			_proceed_closing_scene_tabs();
		} break;
		case FILE_CLOSE: {
			_scene_tab_closed(editor_data.get_edited_scene());
		} break;
		case SCENE_TAB_CLOSE:
		case FILE_SAVE_SCENE: {
			int scene_idx = (p_option == FILE_SAVE_SCENE) ? -1 : tab_closing_idx;