CVE-2026-43164 udplite: Fix null-ptr-deref in __udp_enqueue_schedule_skb().

In the Linux kernel, the following vulnerability has been resolved: udplite: Fix null-ptr-deref in udpenqueuescheduleskb. syzbot reported null-ptr-deref of udpsksk-udpprodqueue. 0 Since the cited commit, udplibinitsock can fail, as can udpinitsock and udpv6initsock. Let's handle the error in...