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.
"   example:    getblock(getblockhash(0) 1)[tx]\n\n"
                "Results without keys can be queried with an integer in brackets using the parenthesized syntax.\n"
                "   example:    getblock(getblockhash(0),1)[tx][0]\n\n")));
            return;
        }
        if (!RPCConsole::RPCExecuteCommandLine(m_node, result, executableCommand, nullptr, wallet_model)) {
            Q_EMIT reply(RPCConsole::CMD_ERROR, QString("Parse error: unbalanced ' or \""));
            return;
        }
        Q_EMIT reply(RPCConsole::CMD_REPLY, QString::fromStdString(result));
    }
    catch (UniValue& objError)
    {
        try // 
        {
            int code = find_value(objError, "code").get_int();
            std::string message = find_value(objError, "message").get_str();
            Q_EMIT reply(RPCConsole::CMD_ERROR, QString::fromStdString(message) + " (code " + QString::number(code) + ")");
        }
        catch (const std::runtime_error&) // 
        {   // 
            Q_EMIT reply(RPCConsole::CMD_ERROR, QString::fromStdString(objError.write()));
        }
    }
    catch (const std::exception& e)
    {
        Q_EMIT reply(RPCConsole::CMD_ERROR, QString("Error: ") + QString::fromStdString(e.what()));
    }
}
RPCConsole::RPCConsole(interfaces::Node& node, const PlatformStyle *_platformStyle, QWidget *parent) :