nat44_add_del_lb_static_mapping

for (i = 0; i < vec_len (locals); i++)
        {
          m_key.addr = locals[i].addr;
          m_key.port = locals[i].port;
          kv.key = m_key.as_u64;
          kv.value = m - sm->static_mappings;
          clib_bihash_add_del_8_8(&sm->static_mapping_by_local, &kv, 1);
          locals[i].prefix = locals[i - 1].prefix + locals[i].probability;  ==> i-1 may be ~0 when i == 0