Fix crash caused by the regression in 9f8fc7b2

lib/nghttp2_session.c

@@ -3725,10 +3725,10 @@ int nghttp2_session_on_rst_stream_received(nghttp2_session *session,
       return session_handle_invalid_connection(
           session, frame, NGHTTP2_ERR_PROTO, "RST_STREAM: stream in idle");
     }
-  }
-
+  } else {
     /* We may use stream->shut_flags for strict error checking. */
     nghttp2_stream_shutdown(stream, NGHTTP2_SHUT_RD);
+  }
 
   rv = session_call_on_frame_received(session, frame);
   if (rv != 0) {