From e1bf38e096345efd9beccf190bc080d041020ed7 Mon Sep 17 00:00:00 2001
From: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Date: Thu, 5 Dec 2024 20:17:36 +0100
Subject: [PATCH] net: lwip: check if network device is available in do_dhcp

eth_get_dev() returns NULL if no network device is available.
Not checking the return value leads to a crash when the device
pointer is dereferenced.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
(cherry picked from commit d701c6ab4220a3f5e0fdef06720816d67c46f56d)