message: Check accumulator hash against block instead of blockindex
diff: @@ -255,7 +255,7 @@ bool ValidateAccumulatorCheckpoint(const CBlock& block, CBlockIndex* pindex, Acc
  return true;
  }
  - if (pindex->mapAccumulatorHashes != pindex->pprev->mapAccumulatorHashes)
  + if (block.mapAccumulatorHashes != pindex->pprev->mapAccumulatorHashes)
  return error("%s : new accumulator checkpoint generated on a block that is not multiple of 10", __func__);
  return true;
  