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.PreciousBlock(state, params, pindex);
}
bool CChainState::InvalidateBlock(CValidationState& state, const CChainParams& chainparams, CBlockIndex *pindex)
{
    AssertLockHeld(cs_main);
    
    
    
    
    
    bool pindex_was_in_chain = false;
    CBlockIndex *invalid_walk_tip = chainActive.Tip();
    DisconnectedBlockTransactions disconnectpool;
    while (chainActive.Contains(pindex)) {
        pindex_was_in_chain = true;
        
        
        if (!DisconnectTip(state, chainparams, &disconnectpool)) {
            
            
            UpdateMempoolForReorg(disconnectpool, false);
            return false;
        }
    }
    
    
    while (pindex_was_in_chain && invalid_walk_tip != pindex) {
        invalid_walk_tip->nStatus |= BLOCK_FAILED_CHILD;
        setDirtyBlockIndex.insert(invalid_walk_tip);
        setBlockIndexCandidates.erase(invalid_walk_tip);