Fix a little bug.

src/subscription/transports/websocket/mod.rs

@@ -145,11 +145,9 @@ where
 
             // receive msg
             if let Some(ctx) = &mut this.ctx {
-                if !ctx.streams.is_empty() {
                 let mut closed = Vec::new();
 
                 for (id, incoming_stream) in ctx.streams.iter_mut() {
-                        loop {
                     match incoming_stream.as_mut().poll_next(cx) {
                         Poll::Ready(Some(res)) => {
                             if let Some(err) = &res.error {
@@ -183,19 +181,14 @@ where
                                     payload: None,
                                 },
                             );
-                                    break;
-                                }
-                                Poll::Pending => {
-                                    break;
-                                }
                         }
+                        Poll::Pending => {}
                     }
                 }
 
                 for id in closed {
                     ctx.streams.remove(&id);
                 }
-                }
 
                 if !ctx.send_buf.is_empty() {
                     continue;