I can reproduce an issue with master; v0.17.1rc1 works fine.

Steps to reproduce:
- `bitcoin-qt -regtest`
- open Console window
- repeat `generatetoaddress 1 AN_ADDRESS` some times until crash

Crash occurs both on wayland and x11.

[debug.log](https://github.com/bitcoin/bitcoin/files/2690776/debug.log)

[wallets.zip](https://github.com/bitcoin/bitcoin/files/2690781/wallets.zip)
{
#ifdef Q_OS_MAC
    
    appMenuBar = new QMenuBar();
#else
    
    appMenuBar = menuBar();
#endif
    
    QMenu *file = appMenuBar->addMenu(tr("&File"));
    if(walletFrame)
    {
        file->addAction(openAction);
        file->addAction(backupWalletAction);
        file->addAction(signMessageAction);
        file->addAction(verifyMessageAction);
        file->addSeparator();
    }
    file->addAction(quitAction);
    QMenu *settings = appMenuBar->addMenu(tr("&Settings"));
    if(walletFrame)
    {
        settings->addAction(encryptWalletAction);