message: [P2P] Don't process/database undefined sporks
  With the removal of some sporks, we want to avoid processing stale
  messages and adding them to the sporkDB with arbitrary identifiers. This
  will return early if the received spork message doesn't map to a defined
  spork.
diff: @@ -69,6 +69,10 @@ void ProcessSpork(CNode* pfrom, std::string& strCommand, CDataStream& vRecv)
  if (chainActive.Tip() == NULL) return;
  + // Ignore spork messages about unknown/deleted sporks
  + std::string strSpork = sporkManager.GetSporkNameByID(spork.nSporkID);
  + if (strSpork == "Unknown") return;
  +
  uint256 hash = spork.GetHash();
  if (mapSporksActive.count(spork.nSporkID)) {
  if (mapSporksActive[spork.nSporkID].nTimeSigned >= spork.nTimeSigned) {
  