### 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
List<String>::Element *E = tabs_to_close.front();
	if (!E) {
		if (_is_closing_editor()) {
			current_menu_option = tab_closing_menu_option;
			_menu_option_confirm(tab_closing_menu_option, true);
		} else {
			current_menu_option = -1;
			save_confirmation->hide();
		}
		return;
	}
	String scene_to_close = E->get();
	tabs_to_close.pop_front();
	int tab_idx = -1;
	for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
		if (editor_data.get_scene_path(i) == scene_to_close) {
			tab_idx = i;
			break;
		}
	}
	ERR_FAIL_COND(tab_idx < 0);
	_scene_tab_closed(tab_idx);
}
bool EditorNode::_is_closing_editor() const {
	return tab_closing_menu_option == FILE_QUIT || tab_closing_menu_option == RUN_PROJECT_MANAGER || tab_closing_menu_option == RELOAD_CURRENT_PROJECT;
}
void EditorNode::_scene_tab_closed(int p_tab, int p_option) {