add check for channel closed error

Author: JacobBarthelmeh

examples/scpclient/scpclient.c

@@ -313,7 +313,9 @@ THREAD_RETURN WOLFSSH_THREAD scp_client(void* args)
 
     ret = wolfSSH_shutdown(ssh);
     /* do not continue on with shutdown process if peer already disconnected */
-    if (ret != WS_SOCKET_ERROR_E && wolfSSH_get_error(ssh) != WS_SOCKET_ERROR_E) {
+    if (ret != WS_CHANNEL_CLOSED && ret != WS_SOCKET_ERROR_E &&
+            wolfSSH_get_error(ssh) != WS_SOCKET_ERROR_E &&
+            wolfSSH_get_error(ssh) != WS_CHANNEL_CLOSED) {
         if (ret != WS_SUCCESS) {
             err_sys("Sending the shutdown messages failed.");
         }