I think that if a reorg fails due to an error while disconnecting blocks, the node should shut down.

My thought is that if we are trying to switch to a more work chain and something goes wrong before we can even try to validate that more-work chain, then we have a problem that is not related to the chain we're trying to switch to but instead related to our own hardware or software; shutting down and having the user deal with the issue is better than continuing on, when we know there's a more work chain that we're unable to try validating.

This has recently come up on testnet, where unpatched nodes are unable to reorg from the invalid chain containing the duplicate-input-in-a-transaction block, but rather than crash or shutdown they are continuing on the invalid chain, with messages like this in the debug log:

```
ERROR: DisconnectTip(): DisconnectBlock 00000000210004840364b52bc5e455d888f164e4264a4fec06a514b67e9d5722 failed
```
return g_chainstate.ActivateBestChain(state, chainparams, std::move(pblock));
}
bool CChainState::PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex)
{
    {
        LOCK(cs_main);
        if (pindex->nChainWork < chainActive.Tip()->nChainWork) {
            
            return true;
        }
        if (chainActive.Tip()->nChainWork > nLastPreciousChainwork) {
            
            nBlockReverseSequenceId = -1;
        }
        nLastPreciousChainwork = chainActive.Tip()->nChainWork;
        setBlockIndexCandidates.erase(pindex);
        pindex->nSequenceId = nBlockReverseSequenceId;
        if (nBlockReverseSequenceId > std::numeric_limits<int32_t>::min()) {
            
            
            nBlockReverseSequenceId--;
        }
        if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && pindex->HaveTxsDownloaded()) {
            setBlockIndexCandidates.insert(pindex);
            PruneBlockIndexCandidates();
        }
    }
    return ActivateBestChain(state, params, std::shared_ptr<const CBlock>());
}
bool PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex) {