A call to `removeprunedfunds` does not update the transaction list in the GUI, and trying to access the info of a deleted transaction will result in a segfault.

```bash
(lldb) run
Process 4859 launched: '/Users/michael/github/bitcoin/src/qt/bitcoin-qt' (x86_64)
2019-09-24 15:41:53.763094+0800 bitcoin-qt[4859:390268] MessageTracer: Falling back to default whitelist
Process 4859 stopped
* thread #1, name = 'bitcoin-main', queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x34)
    frame #0: 0x00000001001c9bf6 bitcoin-qt`TransactionDesc::FormatTxStatus(wtx=0x00007ffeefbfc0e0, status=0x00007ffeefbfc0c0, inMempool=false, numBlocks=1) at transactiondesc.cpp:33:31
   30  	{
   31  	    if (!status.is_final)
   32  	    {
-> 33  	        if (wtx.tx->nLockTime < LOCKTIME_THRESHOLD)
   34  	            return tr("Open for %n more block(s)", "", wtx.tx->nLockTime - numBlocks);
   35  	        else
   36  	            return tr("Open until %1").arg(GUIUtil::dateTimeStr(wtx.tx->nLockTime));
Target 0: (bitcoin-qt) stopped.
```
}
    
    if (mapKeyFirstBlock.empty())
        return;
    
    for (const auto& entry : mapWallet) {
        
        const CWalletTx &wtx = entry.second;
        if (Optional<int> height = locked_chain.getBlockHeight(wtx.m_confirm.hashBlock)) {
            
            for (const CTxOut &txout : wtx.tx->vout) {
                
                for (const auto &keyid : GetAffectedKeys(txout.scriptPubKey, *this)) {
                    
                    std::map<CKeyID, int>::iterator rit = mapKeyFirstBlock.find(keyid);
                    if (rit != mapKeyFirstBlock.end() && *height < rit->second)
                        rit->second = *height;
                }
            }
        }
    }
    
    for (const auto& entry : mapKeyFirstBlock)
        mapKeyBirth[entry.first] = locked_chain.getBlockTime(entry.second) - TIMESTAMP_WINDOW; 
}
/**
 * Compute smart timestamp for a transaction being added to the wallet.
 *
 * Logic:
 * - If sending a transaction, assign its timestamp to the current time.