### Godot version

4.1.3 stable.arch_linux

### System information

Artix Linux Godot v4.1.3 stable.arch_linux

### Issue description

![2023-11-14T16:29:28,788232528+01:00](https://github.com/godotengine/godot/assets/92468390/a79027e2-1539-4ca9-9369-978c32dea26d)
Both "Target Surface:" and "Source Mesh:" accept non Node3D nodes which doesn't really make any sense as they need 3D geometry to function.

### Steps to reproduce

1. Add a MultiMeshInstance3D
2. Add a Node that doesn't inherit Node3D
3. Open the "Populate Surface" menu and click the right button of either "Target Surface:" or "Source Mesh:"

### Minimal reproduction project

N/A
populate_scale_random = memnew(SpinBox);
	populate_scale_random->set_min(0);
	populate_scale_random->set_max(1);
	populate_scale_random->set_value(0);
	populate_scale_random->set_step(0.01);
	vbc->add_margin_child(TTR("Random Scale:"), populate_scale_random);
	populate_scale = memnew(SpinBox);
	populate_scale->set_min(0.001);
	populate_scale->set_max(4096);
	populate_scale->set_value(1);
	populate_scale->set_step(0.01);
	vbc->add_margin_child(TTR("Scale:"), populate_scale);
	populate_amount = memnew(SpinBox);
	populate_amount->set_anchor(SIDE_RIGHT, ANCHOR_END);
	populate_amount->set_begin(Point2(20, 232));
	populate_amount->set_end(Point2(-5, 237));
	populate_amount->set_min(1);
	populate_amount->set_max(65536);
	populate_amount->set_value(128);
	vbc->add_margin_child(TTR("Amount:"), populate_amount);
	populate_dialog->set_ok_button_text(TTR("Populate"));
	populate_dialog->get_ok_button()->connect("pressed", callable_mp(this, &MultiMeshEditor::_populate));
	std = memnew(SceneTreeDialog);
	populate_dialog->add_child(std);
	std->connect("selected", callable_mp(this, &MultiMeshEditor::_browsed));
	_last_pp_node = nullptr;
	err_dialog = memnew(AcceptDialog);
	add_child(err_dialog);
}
void MultiMeshEditorPlugin::edit(Object *p_object) {