virtio-console: fix uninitialized rx virtqueue pointer

Author: Aphlita

components/drivers/virtio/virtio_console.c

@@ -617,7 +617,9 @@ static void virtio_console_isr(int irqno, void *param)
     {
         rt_uint32_t queue_rx_index = port_dev->queue_rx_index;
         struct virtq *queue_rx = port_dev->queue_rx;
-
+        struct virtqueue *queue_rx = port_dev->rx_vq;
+        if (!queue_rx)
+            return;
 #ifdef RT_USING_SMP
         rt_base_t level = rt_spin_lock_irqsave(&port_dev->spinlock_rx);
 #endif