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)

{
    assert(!m_wallet_controller);
    assert(wallet_controller);
    m_wallet_controller = wallet_controller;
    m_create_wallet_action->setEnabled(true);
    m_open_wallet_action->setEnabled(true);
    m_open_wallet_action->setMenu(m_open_wallet_menu);
    connect(wallet_controller, &WalletController::walletAdded, this, &BitcoinGUI::addWallet);
    connect(wallet_controller, &WalletController::walletRemoved, this, &BitcoinGUI::removeWallet);
    for (WalletModel* wallet_model : m_wallet_controller->getOpenWallets()) {
        addWallet(wallet_model);
    }
}
void BitcoinGUI::addWallet(WalletModel* walletModel)