netfilter: ipset: drop logically empty buckets in mtype_del

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CVE-2026-31418

In the Linux kernel, the following vulnerability has been resolved: netfilter: ipset: drop logically empty buckets in mtypedel mtypedel counts empty slots below n-pos in k, but it only drops the bucket when both n-pos and k are zero. This misses buckets whose live entries have all been removed...