### 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)

String s = get_edited_property_value();
	property->set_text(s);
	selected_type = s;
}
void EditorPropertyClassName::_property_selected() {
	dialog->popup_create(true);
}
void EditorPropertyClassName::_dialog_created() {
	selected_type = dialog->get_selected_type();
	emit_changed(get_edited_property(), selected_type);
	update_property();
}
void EditorPropertyClassName::_bind_methods() {
}
EditorPropertyClassName::EditorPropertyClassName() {
	property = memnew(Button);
	property->set_clip_text(true);
	add_child(property);
	add_focusable(property);
	property->set_text(selected_type);
	property->connect("pressed", callable_mp(this, &EditorPropertyClassName::_property_selected));
	dialog = memnew(CreateDialog);
	dialog->set_base_type(base_type);
	dialog->connect("create", callable_mp(this, &EditorPropertyClassName::_dialog_created));
	add_child(dialog);
}
void EditorPropertyCheck::_set_read_only(bool p_read_only) {