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
```
int64_t nSigOpsCost = GetTransactionSigOpCost(tx, view, STANDARD_SCRIPT_VERIFY_FLAGS);
        
        CAmount nModifiedFees = nFees;
        pool.ApplyDelta(hash, nModifiedFees);
        
        
        bool fSpendsCoinbase = false;
        for (const CTxIn &txin : tx.vin) {
            const Coin &coin = view.AccessCoin(txin.prevout);
            if (coin.IsCoinBase()) {
                fSpendsCoinbase = true;
                break;
            }
        }
        CTxMemPoolEntry entry(ptx, nFees, nAcceptTime, chainActive.Height(),
                              fSpendsCoinbase, nSigOpsCost, lp);
        unsigned int nSize = entry.GetTxSize();
        
        
        
        
        
        if (nSigOpsCost > MAX_STANDARD_TX_SIGOPS_COST)
            return state.DoS(0, false, REJECT_NONSTANDARD, "bad-txns-too-many-sigops", false,
                strprintf("%d", nSigOpsCost));
        CAmount mempoolRejectFee = pool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFee(nSize);
        if (!bypass_limits && mempoolRejectFee > 0 && nModifiedFees < mempoolRejectFee) {
            return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "mempool min fee not met", false, strprintf("%d < %d", nModifiedFees, mempoolRejectFee));
        }