Using master. During startup, if you open `Window` -> `Console` and try and execute any command (can be garbage) `bitcoin-qt` will crash:
```bash
On branch pull/16118/local-merge

Process 89287 launched: '/Users/michael/github/bitcoin/src/qt/bitcoin-qt' (x86_64)
2019-05-29 09:57:56.276746-0400 bitcoin-qt[89287:939924] MessageTracer: Falling back to default whitelist
Process 89287 stopped
* thread #1, name = 'bitcoin-main', queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x8)
    frame #0: 0x00000001015158ba QtWidgets`QCompleter::popup() const + 10
QtWidgets`QCompleter::popup:
->  0x1015158ba <+10>: movq   0x8(%rdi), %rbx
    0x1015158be <+14>: movq   0x88(%rbx), %rax
    0x1015158c5 <+21>: testq  %rax, %rax
    0x1015158c8 <+24>: jne    0x101515942               ; <+146>
Target 0: (bitcoin-qt) stopped.
```

Not sure if just disabling the menu, like in #16118 would be ok, as a user might actually want to be able to run a command.
{
    ui->mempoolNumberTxs->setText(QString::number(numberOfTxs));
    if (dynUsage < 1000000)
        ui->mempoolSize->setText(QString::number(dynUsage/1000.0, 'f', 2) + " KB");
    else
        ui->mempoolSize->setText(QString::number(dynUsage/1000000.0, 'f', 2) + " MB");
}
void RPCConsole::on_lineEdit_returnPressed()
{
    QString cmd = ui->lineEdit->text();
    if(!cmd.isEmpty())
    {
        std::string strFilteredCmd;
        try {
            std::string dummy;
            if (!RPCParseCommandLine(nullptr, dummy, cmd.toStdString(), false, &strFilteredCmd)) {
                // F
                throw std::runtime_error("Invalid command line");
            }
        } catch (const std::exception& e) {
            QMessageBox::critical(this, "Error", QString("Error: ") + QString::fromStdString(e.what()));
            return;
        }
        ui->lineEdit->clear();
        cmdBeforeBrowsing = QString();
        WalletModel* wallet_model{nullptr};
#ifdef ENABLE_WALLET