### 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
node = p_multimesh;
}
void MultiMeshEditor::_browse(bool p_source) {
	browsing_source = p_source;
	std->get_scene_tree()->set_marked(node, false);
	std->popup_scenetree_dialog();
	if (p_source) {
		std->set_title(TTR("Select a Source Mesh:"));
	} else {
		std->set_title(TTR("Select a Target Surface:"));
	}
}
void MultiMeshEditor::_bind_methods() {
}
MultiMeshEditor::MultiMeshEditor() {
	options = memnew(MenuButton);
	options->set_switch_on_hover(true);
	Node3DEditor::get_singleton()->add_control_to_menu_panel(options);
	options->set_text("MultiMesh");
	options->set_icon(EditorNode::get_singleton()->get_editor_theme()->get_icon(SNAME("MultiMeshInstance3D"), EditorStringName(EditorIcons)));
	options->get_popup()->add_item(TTR("Populate Surface"));
	options->get_popup()->connect("id_pressed", callable_mp(this, &MultiMeshEditor::_menu_option));
	populate_dialog = memnew(ConfirmationDialog);
	populate_dialog->set_title(TTR("Populate MultiMesh"));
	add_child(populate_dialog);
	VBoxContainer *vbc = memnew(VBoxContainer);
	populate_dialog->add_child(vbc);
	
	HBoxContainer *hbc = memnew(HBoxContainer);
	surface_source = memnew(LineEdit);