### 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 = EDITOR_GET("interface/inspector/horizontal_vector_types_editing");
	VBoxContainer *bc = memnew(VBoxContainer);
	edit_custom_bc = memnew(VBoxContainer);
	BoxContainer *edit_custom_layout;
	if (horizontal) {
		default_layout = memnew(HBoxContainer);
		edit_custom_layout = memnew(HBoxContainer);
		set_bottom_editor(bc);
	} else {
		default_layout = memnew(VBoxContainer);
		edit_custom_layout = memnew(VBoxContainer);
	}
	edit_custom_bc->hide();
	add_child(bc);
	edit_custom_bc->set_h_size_flags(SIZE_EXPAND_FILL);
	default_layout->set_h_size_flags(SIZE_EXPAND_FILL);
	edit_custom_layout->set_h_size_flags(SIZE_EXPAND_FILL);
	bc->add_child(default_layout);
	bc->add_child(edit_custom_bc);
	static const char *desc[4] = { "x", "y", "z", "w" };
	for (int i = 0; i < 4; i++) {
		spin[i] = memnew(EditorSpinSlider);
		spin[i]->set_flat(true);