Compile master, and run with `src/qt/bitcoin-qt -regtest -nowallet`. As expected, no icon is displayed. Load and unload a wallet. The `HD` icon remains.

On startup:
![on_startup](https://user-images.githubusercontent.com/863730/72410834-711b4c00-37a4-11ea-9a10-bfcf3db7ce68.png)

After a wallet load and unload:
![after_load_unload](https://user-images.githubusercontent.com/863730/72410838-737da600-37a4-11ea-8854-dd13301c0135.png)

QMainWindow(parent),
    m_node(node),
    trayIconMenu{new QMenu()},
    platformStyle(_platformStyle),
    m_network_style(networkStyle)
{
    QSettings settings;
    if (!restoreGeometry(settings.value("MainWindowGeometry").toByteArray())) {
        
        move(QGuiApplication::primaryScreen()->availableGeometry().center() - frameGeometry().center());
    }
#ifdef ENABLE_WALLET
    enableWallet = WalletModel::isWalletEnabled();
#endif 
    QApplication::setWindowIcon(m_network_style->getTrayAndWindowIcon());
    setWindowIcon(m_network_style->getTrayAndWindowIcon());
    updateWindowTitle();
    rpcConsole = new RPCConsole(node, _platformStyle, nullptr);
    helpMessageDialog = new HelpMessageDialog(node, this, false);
#ifdef ENABLE_WALLET
    if(enableWallet)
    {
        
        walletFrame = new WalletFrame(_platformStyle, this);
        setCentralWidget(walletFrame);
    } else
#endif 
    {
        /* When compiled without wallet or -disablewallet is provided,