[net][udp] fix udp wrb-iob leak when NIC was down

Signed-off-by: meijian <meijian@xiaomi.com>

net/udp/udp_sendto_buffered.c

@@ -151,12 +151,6 @@ static void sendto_writebuffer_release(FAR struct udp_conn_s *conn)
           wrb = (FAR struct udp_wrbuffer_s *)sq_remfirst(&conn->write_q);
           DEBUGASSERT(wrb != NULL);
 
-          /* Do not need to release wb_iob, the life cycle of wb_iob is
-           * handed over to the network device
-           */
-
-          wrb->wb_iob = NULL;
-
           udp_wrbuffer_release(wrb);
 
           /* Set up for the next packet transfer by setting the connection
@@ -455,6 +449,12 @@ static uint16_t sendto_eventhandler(FAR struct net_driver_s *dev,
       dev->d_sndlen = wrb->wb_iob->io_pktlen - udpiplen;
       ninfo("wrb=%p sndlen=%d\n", wrb, dev->d_sndlen);
 
+      /* Do not need to release wb_iob, the life cycle of wb_iob is
+       * handed over to the network device
+       */
+
+      wrb->wb_iob = NULL;
+
 #ifdef NEED_IPDOMAIN_SUPPORT
       /* If both IPv4 and IPv6 support are enabled, then we will need to
        * select which one to use when generating the outgoing packet.