I keep getting this error when making RPC calls with this library. ```rust pub async fn fetch_new_blocks() -> Result<(), Box<dyn Error>> { let rpc_url = "rpc_url"; let client = Client::new(&rpc_url, Auth::None).expect("Failed to create client"); let best_block_hash = client.get_best_block_hash()?; println!("best block hash: {}", best_block_hash); let current_height = client.get_block_count()?; println!("{}", current_height); Ok(()) } ``` Error: `JSON-RPC error: transport error: unexpected HTTP code: 400` PS: My RPC URL does not have a username and password. The URL contains a token for auth