message: validation: don't try to invalidate genesis block
diff: @@ -2812,6 +2812,10 @@ bool CChainState::PreciousBlock(BlockValidationState& state, const CChainParams&
  bool CChainState::InvalidateBlock(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex *pindex)
  {
  + // Genesis block can't be invalidated
  + assert(pindex);
  + if (pindex->nHeight == 0) return false;
  +
  CBlockIndex* to_mark_failed = pindex;
  bool pindex_was_in_chain = false;
  int disconnected = 0;
  