### 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)

use_sub_inspector = p_enable;
}
void EditorPropertyResource::fold_resource() {
	bool unfolded = get_edited_object()->editor_is_section_unfolded(get_edited_property());
	if (unfolded) {
		resource_picker->set_toggle_pressed(false);
		get_edited_object()->editor_set_section_unfold(get_edited_property(), false);
		update_property();
	}
}
void EditorPropertyResource::_notification(int p_what) {
	switch (p_what) {
		case NOTIFICATION_ENTER_TREE:
		case NOTIFICATION_THEME_CHANGED: {
			if (!updating_theme) {
				_update_property_bg();
			}
		} break;
		case NOTIFICATION_EXIT_TREE: {
			const EditorInspector *ei = get_parent_inspector();
			if (ei && !ei->is_main_editor_inspector()) {
				fold_resource();
			}
		} break;
	}
}
EditorPropertyResource::EditorPropertyResource() {