fix: create ref for SealCube

src/app/page.tsx

@@ -600,6 +600,7 @@ export default function Home() {
 	// 	}
 	// );
 
+	const [sealMesh, setSealMesh] = useState<Mesh | null>(null);
 	return (
 		<Canvas
 			shadows
@@ -635,8 +636,8 @@ export default function Home() {
 				grassSize={0.6}
 				grassLOD={80}
 			/>
+			<SealCube ref={(mesh) => { if (mesh && !sealMesh) setSealMesh(mesh) }} />
 
-			<SealCube />
 			<OrbitControls
 				target={[0, 5, 0]}
 				enablePan={false}