### 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
callable_mp_static(&EditorNode::_file_access_close_error_notify_impl).bind(p_str).call_deferred();
}
void EditorNode::_file_access_close_error_notify_impl(const String &p_str) {
	add_io_error(vformat(TTR("Unable to write to file '%s', file in use, locked or lacking permissions."), p_str));
}
void EditorNode::reload_scene(const String &p_path) {