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
```
assert(!(pindex->nStatus & BLOCK_HAVE_DATA) == (pindex->nTx == 0));
            assert(pindexFirstMissing == pindexFirstNeverProcessed);
        } else {
            
            if (pindex->nStatus & BLOCK_HAVE_DATA) assert(pindex->nTx > 0);
        }
        if (pindex->nStatus & BLOCK_HAVE_UNDO) assert(pindex->nStatus & BLOCK_HAVE_DATA);
        assert(((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_TRANSACTIONS) == (pindex->nTx > 0)); 
        
        assert((pindexFirstNeverProcessed == nullptr) == pindex->HaveTxsDownloaded());
        assert((pindexFirstNotTransactionsValid == nullptr) == pindex->HaveTxsDownloaded());
        assert(pindex->nHeight == nHeight); 
        assert(pindex->pprev == nullptr || pindex->nChainWork >= pindex->pprev->nChainWork); 
        assert(nHeight < 2 || (pindex->pskip && (pindex->pskip->nHeight < nHeight))); 
        assert(pindexFirstNotTreeValid == nullptr); 
        if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_TREE) assert(pindexFirstNotTreeValid == nullptr); 
        if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_CHAIN) assert(pindexFirstNotChainValid == nullptr); 
        if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_SCRIPTS) assert(pindexFirstNotScriptsValid == nullptr); 
        if (pindexFirstInvalid == nullptr) {
            
            assert((pindex->nStatus & BLOCK_FAILED_MASK) == 0); 
        }
        if (!CBlockIndexWorkComparator()(pindex, chainActive.Tip()) && pindexFirstNeverProcessed == nullptr) {
            if (pindexFirstInvalid == nullptr) {
                
                
                
                
                if (pindexFirstMissing == nullptr || pindex == chainActive.Tip()) {
                    assert(setBlockIndexCandidates.count(pindex));