### 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
multimesh_editor->edit(Object::cast_to<MultiMeshInstance3D>(p_object));
}
bool MultiMeshEditorPlugin::handles(Object *p_object) const {
	return p_object->is_class("MultiMeshInstance3D");
}
void MultiMeshEditorPlugin::make_visible(bool p_visible) {
	if (p_visible) {
		multimesh_editor->options->show();
	} else {
		multimesh_editor->options->hide();
		multimesh_editor->edit(nullptr);
	}
}
MultiMeshEditorPlugin::MultiMeshEditorPlugin() {
	multimesh_editor = memnew(MultiMeshEditor);
	EditorNode::get_singleton()->get_main_screen_control()->add_child(multimesh_editor);
	multimesh_editor->options->hide();
}
MultiMeshEditorPlugin::~MultiMeshEditorPlugin() {
}