### 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<Node *> nodes_owned_by_original_node;
				original_node->get_owned_by(original_node, &nodes_owned_by_original_node);
				for (Node *owned_node : nodes_owned_by_original_node) {
					owned_node->set_owner(nullptr);
				}
				
				while (original_node->get_child_count()) {
					Node *child = original_node->get_child(0);
					original_node->remove_child(child);
					child->queue_free();
				}
				
				bool is_editable = true;
				Node *owner = original_node->get_owner();
				if (owner) {
					is_editable = owner->is_editable_instance(original_node);
				}
				
				Ref<PackedScene> current_packed_scene;
				if (original_node->get_scene_file_path() == p_instance_path) {
					
					
					current_packed_scene = instance_scene_packed_scene;
				} else {
					
					
					List<String> required_load_paths;
					String scene_path = original_node->get_scene_file_path();