fix: test case error

Author: xianml

uvicorn/server.py

@@ -263,8 +263,9 @@ async def shutdown(self, sockets: list[socket.socket] | None = None) -> None:
         logger.info("Shutting down")
 
         # Stop accepting new connections.
-        for server in self.servers:
-            server.close()
+        if hasattr(self, "servers") and self.servers:
+            for server in self.servers:
+                server.close()
         for sock in sockets or []:
             sock.close()  # pragma: full coverage