fuzzer reports crash in qp.c

qp.c:2000:6: runtime error: index -1 out of bounds for type 'struct (unnamed struct at ./include/dns/qp.h:247:2)[128]'
    #0 0x722b59 in add_link bind9/lib/dns/qp.c:2000:35
    #1 0x7225a1 in dns_qp_lookup bind9/lib/dns/qp.c:2168:3
    #2 0x66e71e in dns_zt_find bind9/lib/dns/zt.c:181:11
    #3 0x5eae24 in dns_view_find bind9/lib/dns/view.c:850:12
    #4 0x5ebb14 in dns_view_simplefind bind9/lib/dns/view.c:1061:11
    #5 0x4f38e8 in dns_message_checksig bind9/lib/dns/message.c:3168:12