### Godot version

4.0-rc6

### System information

Fedora 37, Mesa Intel ADL GT2

### Issue description

Code that works as expected at runtime fails with Nil references to (assigned) exported vars in the editor:

![tool_global_position_error](https://user-images.githubusercontent.com/364501/222031460-ffb1ecbd-5175-4a42-8470-25285ba5f821.png)


### Steps to reproduce

Try to access the `global_position` of a `Node3D` that's assigned to an exported var.

See that it works at runtime.

See that it errors in the editor with:

> Invalid get index 'global_position' (on base: 'Nil').

### Minimal reproduction project

[tool_test.zip](https://github.com/godotengine/godot/files/10856640/tool_test.zip)

nd.owner = 0;
	} else {
		nd.owner = -1;
	}
	MissingNode *missing_node = Object::cast_to<MissingNode>(p_node);
	
	
	if (states_stack.is_empty() && !is_editable_instance) {
		
		if (missing_node != nullptr) {
			
			nd.type = _nm_get_string(missing_node->get_original_class(), name_map);
		} else {
			nd.type = _nm_get_string(p_node->get_class(), name_map);
		}
	} else {
		
		
		nd.type = TYPE_INSTANTIATED;
	}
	
	
	
	
	
	bool save_node = nd.properties.size() || nd.groups.size(); 
	save_node = save_node || p_node == p_owner; 
	save_node = save_node || (p_node->get_owner() == p_owner && instantiated_by_owner); 
	int idx = nodes.size();