<!-- Describe the issue -->

When our chainstate activation sequence fails and we're running the GUI, we ask the user via a question box whether or not they'd like to re-run the sequence with `fReindex = true`. Fun fact: despite the fact that this sequence is wrapped in a while loop, we only run it twice at most.

https://github.com/bitcoin/bitcoin/blob/7ecb309c4ed1bb9ae6b9a12cbb4f083328edc125/src/init.cpp#L1539-L1556

If they answer yes, the sequence will always fail, because a chainstate will have already been initialized in the original run and `InitializeChainstate` will throw a `std::logic_error`:

https://github.com/bitcoin/bitcoin/blob/7ecb309c4ed1bb9ae6b9a12cbb4f083328edc125/src/validation.cpp#L4573-L4594

This always reproduces. To reproduce:
```
gdb ./src/qt/bitcoin-qt
(gdb) b InitializeChainstate
(gdb) # add breakpoint for the "if (!fLoaded && !ShutdownRequested()) {" line
(gdb) r  # should stop at the breakpoint for InitializeChainstate
(gdb) c  # to advance to the breakpoint for the "if (!fLoaded && !ShutdownRequested()) {" line
(gdb) set fLoaded=false
(gdb) c  # should stop at the breakpoint for InitializeChainstate
(gdb) n  # step through InitializeChainstate to see that it throws
```

We expect the re-run of the chainstate activation sequence to not always fail.

{
    return BlockFileSeq().Open(pos, fReadOnly);
}
static FILE* OpenUndoFile(const FlatFilePos& pos, bool fReadOnly)
{
    return UndoFileSeq().Open(pos, fReadOnly);
}
fs::path GetBlockPosFilename(const FlatFilePos& pos)
{
    return BlockFileSeq().FileName(pos);
}
bool BlockManager::FindBlockPos(FlatFilePos& pos, unsigned int nAddSize, unsigned int nHeight, CChain& active_chain, uint64_t nTime, bool fKnown)
{
    LOCK(cs_LastBlockFile);
    unsigned int nFile = fKnown ? pos.nFile : m_last_blockfile;
    if (m_blockfile_info.size() <= nFile) {
        m_blockfile_info.resize(nFile + 1);
    }
    bool finalize_undo = false;
    if (!fKnown) {
        while (m_blockfile_info[nFile].nSize + nAddSize >= (gArgs.GetBoolArg("-fastprune", false) ? 0x10000  : MAX_BLOCKFILE_SIZE)) {
            
            
            
            finalize_undo = (m_blockfile_info[nFile].nHeightLast == (unsigned int)active_chain.Tip()->nHeight);
            nFile++;
            if (m_blockfile_info.size() <= nFile) {
                m_blockfile_info.resize(nFile + 1);
            }
        }