fix: avoid webchat stream result crash on queue errors (#6123)

Co-authored-by: stablegenius49 <185121704+stablegenius49@users.noreply.github.com>

astrbot/dashboard/routes/chat.py

@@ -36,6 +36,20 @@ async def track_conversation(convs: dict, conv_id: str):
         convs.pop(conv_id, None)
 
 
+async def _poll_webchat_stream_result(back_queue, username: str):
+    try:
+        result = await asyncio.wait_for(back_queue.get(), timeout=1)
+    except asyncio.TimeoutError:
+        return None, False
+    except asyncio.CancelledError:
+        logger.debug(f"[WebChat] 用户 {username} 断开聊天长连接。")
+        return None, True
+    except Exception as e:
+        logger.error(f"WebChat stream error: {e}")
+        return None, False
+    return result, False
+
+
 class ChatRoute(Route):
     def __init__(
         self,
@@ -343,16 +357,12 @@ class ChatRoute(Route):
 
                 async with track_conversation(self.running_convs, webchat_conv_id):
                     while True:
-                        try:
-                            result = await asyncio.wait_for(back_queue.get(), timeout=1)
-                        except asyncio.TimeoutError:
-                            continue
-                        except asyncio.CancelledError:
-                            logger.debug(f"[WebChat] 用户 {username} 断开聊天长连接。")
+                        result, should_break = await _poll_webchat_stream_result(
+                            back_queue, username
+                        )
+                        if should_break:
                             client_disconnected = True
-                        except Exception as e:
-                            logger.error(f"WebChat stream error: {e}")
-
+                            break
                         if not result:
                             continue