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.
{
    setFontSize(consoleFontSize+1);
}
void RPCConsole::fontSmaller()
{
    setFontSize(consoleFontSize-1);
}
void RPCConsole::setFontSize(int newSize)
{
    QSettings settings;
    //
    if (newSize < FONT_RANGE.width() || newSize > FONT_RANGE.height())
        return;
    // 
    QString str = ui->messagesWidget->toHtml();
    // 
    str.replace(QString("font-size:%1pt").arg(consoleFontSize), QString("font-size:%1pt").arg(newSize));
    // 
    consoleFontSize = newSize;
    settings.setValue(fontSizeSettingsKey, consoleFontSize);
    // 
    float oldPosFactor = 1.0 / ui->messagesWidget->verticalScrollBar()->maximum() * ui->messagesWidget->verticalScrollBar()->value();
    clear(false);
    ui->messagesWidget->setHtml(str);
    ui->messagesWidget->verticalScrollBar()->setValue(oldPosFactor * ui->messagesWidget->verticalScrollBar()->maximum());
}
void RPCConsole::clear(bool clearHistory)