### 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
}
	
	for (int i = 0; i < index_sets.size(); i++) {
		RBSet<int> iset = index_sets[i];
		while (iset.size() > 1) {
			
			for (const int &E : iset) {
				int set_idx = E;
				String scene_name = r_filenames[set_idx];
				String full_path = p_full_paths[set_idx];
				
				scene_name = scene_name.get_basename();
				if (full_path.begins_with("res:")) {
					full_path = full_path.substr(6);
				}
				full_path = full_path.get_basename();
				
				scene_name = scene_name.trim_suffix("/");
				full_path = full_path.trim_suffix("/");
				int scene_name_size = scene_name.size();
				int full_path_size = full_path.size();
				int difference = full_path_size - scene_name_size;
				
				
				
				
				if (difference > 0) {
					String parent = full_path.substr(0, difference);
					int slash_idx = parent.rfind("/");
					slash_idx = parent.rfind("/", slash_idx - 1);