message: Fix bug on AcceptBlock when pindex is null
diff: @@ -4428,7 +4428,7 @@ bool ContextualCheckZerocoinStake(int nHeight, CStakeInput* stake)
  return error("%s: failed to get index associated with zPIV stake checksum", __func__);
  if (chainActive.Height() - pindexFrom->nHeight < Params().Zerocoin_RequiredStakeDepth())
  - return error("%s: zPIV stake does not have required confirmation depth", __func__);
  + return error("%s: zPIV stake does not have required confirmation depth. Current height %d, stakeInput height %d.", __func__, chainActive.Height(), pindexFrom->nHeight);
  //The checksum needs to be the exact checksum from 200 blocks ago
  uint256 nCheckpoint200 = chainActive[nHeight - Params().Zerocoin_RequiredStakeDepth()]->nAccumulatorCheckpoint;
  @@ -4828,7 +4828,7 @@ bool ProcessNewBlock(CValidationState& state, CNode* pfrom, CBlock* pblock, CDis
  CheckBlockIndex ();
  if (!ret) {
  // Check spamming
  - if(pfrom && GetBoolArg("-blockspamfilter", DEFAULT_BLOCK_SPAM_FILTER)) {
  + if(pindex && pfrom && GetBoolArg("-blockspamfilter", DEFAULT_BLOCK_SPAM_FILTER)) {
  CNodeState *nodestate = State(pfrom->GetId());
  if(nodestate != nullptr) {
  nodestate->nodeBlocks.onBlockReceived(pindex->nHeight);
  @@ -4847,6 +4847,9 @@ bool ProcessNewBlock(CValidationState& state, CNode* pfrom, CBlock* pblock, CDis
  }
  return error("%s : AcceptBlock FAILED", __func__);
  }
  + else {
  + LogPrintf("%s : AccpetBlock PASSED!", __func__);
  + }
  }
  if (!ActivateBestChain(state, pblock, checked))
  