rvsttd: fix SocketAddr Default trait bound

rvsttd/src/main.rs

@@ -521,7 +521,7 @@ fn main() -> Result<()> {
         };
 
         stream.set_nodelay(true).ok();
-        log(&format!("Client connected: {}", stream.peer_addr().unwrap_or_default()));
+        log(&format!("Client connected: {}", stream.peer_addr().map(|a| a.to_string()).unwrap_or_else(|_| "?".to_string())));
 
         let writer_stream = stream.try_clone()?;
         let reader = BufReader::new(stream);