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
```
{
    AssertLockNotHeld(cs_main);
    {
        CBlockIndex *pindex = nullptr;
        if (fNewBlock) *fNewBlock = false;
        CValidationState state;
        
        
        LOCK(cs_main);
        
        
        bool ret = CheckBlock(*pblock, state, chainparams.GetConsensus());
        if (ret) {
            
            ret = g_chainstate.AcceptBlock(pblock, state, chainparams, &pindex, fForceProcessing, nullptr, fNewBlock);
        }
        if (!ret) {
            GetMainSignals().BlockChecked(*pblock, state);
            return error("%s: AcceptBlock FAILED (%s)", __func__, FormatStateMessage(state));
        }
    }
    NotifyHeaderTip();
    CValidationState state; 
    if (!g_chainstate.ActivateBestChain(state, chainparams, pblock))
        return error("%s: ActivateBestChain failed (%s)", __func__, FormatStateMessage(state));
    return true;
}
bool TestBlockValidity(CValidationState& state, const CChainParams& chainparams, const CBlock& block, CBlockIndex* pindexPrev, bool fCheckPOW, bool fCheckMerkleRoot)