### 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)

for (int i = 0; i < 4; i++) {
		spin[i]->set_read_only(p_read_only);
	}
	for (int i = 0; i < 3; i++) {
		euler[i]->set_read_only(p_read_only);
	}
}
void EditorPropertyQuaternion::_edit_custom_value() {
	if (edit_button->is_pressed()) {
		edit_custom_bc->show();
		for (int i = 0; i < 3; i++) {
			euler[i]->grab_focus();
		}
	} else {
		edit_custom_bc->hide();
		for (int i = 0; i < 4; i++) {
			spin[i]->grab_focus();
		}
	}
	update_property();
}
void EditorPropertyQuaternion::_custom_value_changed(double val) {