net_sched: hfsc: Fix a potential UAF in hfsc_dequeue() too

net_sched: hfsc: Fix a potential UAF in hfsc_dequeue() too

Similarly to the previous patch, we need to safe guard hfsc_dequeue()
too. But for this one, we don't have a reliable reproducer.

Fixes: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ("Linux-2.6.12-rc2")
Reported-by: Gerrard Tai <gerrard.tai@starlabs.sg>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/20250417184732.943057-3-xiyou.wangcong@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>