### 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)

bool horizontal = p_force_wide || bool(EDITOR_GET("interface/inspector/horizontal_vector_types_editing"));
	BoxContainer *bc;
	if (p_force_wide) {
		bc = memnew(HBoxContainer);
		add_child(bc);
	} else if (horizontal) {
		bc = memnew(HBoxContainer);
		add_child(bc);
		set_bottom_editor(bc);
	} else {
		bc = memnew(VBoxContainer);
		add_child(bc);
	}
	static const char *desc[4] = { "x", "y", "z", "d" };
	for (int i = 0; i < 4; i++) {
		spin[i] = memnew(EditorSpinSlider);
		spin[i]->set_flat(true);
		spin[i]->set_label(desc[i]);
		bc->add_child(spin[i]);
		add_focusable(spin[i]);
		spin[i]->connect("value_changed", callable_mp(this, &EditorPropertyPlane::_value_changed).bind(desc[i]));
		if (horizontal) {
			spin[i]->set_h_size_flags(SIZE_EXPAND_FILL);
		}
	}
	if (!horizontal) {
		set_label_reference(spin[0]); 
	}
}
void EditorPropertyQuaternion::_set_read_only(bool p_read_only) {