OSV-2020-1417 Index-out-of-bounds in DHT::get_hv_rbg

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=23870 Crash type: Index-out-of-bounds Crash state: DHT::gethvrbg DHT::makehvdline DHT::makehvdirs...