### 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
int scene_idx = -1;
	for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
		if (editor_data.get_scene_path(i) == p_path) {
			scene_idx = i;
			break;
		}
	}
	int current_tab = editor_data.get_edited_scene();
	if (scene_idx == -1) {
		if (get_edited_scene()) {
			
			EditorUndoRedoManager::get_singleton()->clear_history(false, editor_data.get_current_edited_scene_history_id());
		}
		return;
	}
	if (current_tab == scene_idx) {
		editor_data.apply_changes_in_editors();
		_save_editor_states(p_path);
	}
	
	_remove_scene(scene_idx, false);
	load_scene(p_path, true, false, true, true);
	
	editor_data.move_edited_scene_to_index(scene_idx);
	EditorUndoRedoManager::get_singleton()->clear_history(false, editor_data.get_scene_history_id(scene_idx));
	
	scene_tabs->set_current_tab(current_tab);
}
void EditorNode::find_all_instances_inheriting_path_in_node(Node *p_root, Node *p_node, const String &p_instance_path, List<Node *> &p_instance_list) {