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<!-- Describe the issue -->
double click bitcoin icon on the task bar with setting 'minimize to the tray' cause a blank window
<!--- What behavior did you expect? -->
![ezgif com-video-to-gif](https://user-images.githubusercontent.com/11154118/38133010-fad94d80-343f-11e8-8bf4-127100e9c1f4.gif)

<!--- What was the actual behavior (provide screenshots if the issue is GUI-related)? -->

<!--- How reliably can you reproduce the issue, what are the steps to do so? -->

<!-- What version of Bitcoin Core are you using, where did you get it (website, self-compiled, etc)? -->

<!-- What type of machine are you observing the error on (OS/CPU and disk type)? -->

<!-- Any extra information that might be useful in the debugging process. -->
<!--- This is normally the contents of a `debug.log` or `config.log` file. Raw text or a link to a pastebin type site are preferred. -->

openAction->setStatusTip(tr("Open a bitcoin: URI or payment request"));
    showHelpMessageAction = new QAction(platformStyle->TextColorIcon(":/icons/info"), tr("&Command-line options"), this);
    showHelpMessageAction->setMenuRole(QAction::NoRole);
    showHelpMessageAction->setStatusTip(tr("Show the %1 help message to get a list with possible Bitcoin command-line options").arg(tr(PACKAGE_NAME)));
    connect(quitAction, SIGNAL(triggered()), qApp, SLOT(quit()));
    connect(aboutAction, SIGNAL(triggered()), this, SLOT(aboutClicked()));
    connect(aboutQtAction, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
    connect(optionsAction, SIGNAL(triggered()), this, SLOT(optionsClicked()));
    connect(toggleHideAction, SIGNAL(triggered()), this, SLOT(toggleHidden()));
    connect(showHelpMessageAction, SIGNAL(triggered()), this, SLOT(showHelpMessageClicked()));
    connect(openRPCConsoleAction, SIGNAL(triggered()), this, SLOT(showDebugWindow()));
    
    connect(quitAction, SIGNAL(triggered()), rpcConsole, SLOT(hide()));
#ifdef ENABLE_WALLET
    if(walletFrame)
    {
        connect(encryptWalletAction, SIGNAL(triggered(bool)), walletFrame, SLOT(encryptWallet(bool)));
        connect(backupWalletAction, SIGNAL(triggered()), walletFrame, SLOT(backupWallet()));
        connect(changePassphraseAction, SIGNAL(triggered()), walletFrame, SLOT(changePassphrase()));
        connect(signMessageAction, SIGNAL(triggered()), this, SLOT(gotoSignMessageTab()));
        connect(verifyMessageAction, SIGNAL(triggered()), this, SLOT(gotoVerifyMessageTab()));
        connect(usedSendingAddressesAction, SIGNAL(triggered()), walletFrame, SLOT(usedSendingAddresses()));
        connect(usedReceivingAddressesAction, SIGNAL(triggered()), walletFrame, SLOT(usedReceivingAddresses()));
        connect(openAction, SIGNAL(triggered()), this, SLOT(openClicked()));
    }
#endif 
    new QShortcut(QKeySequence(Qt::CTRL + Qt::SHIFT + Qt::Key_C), this, SLOT(showDebugWindowActivateConsole()));
    new QShortcut(QKeySequence(Qt::CTRL + Qt::SHIFT + Qt::Key_D), this, SLOT(showDebugWindow()));
}
void BitcoinGUI::createMenuBar()