<!-- This issue tracker is only for technical issues related to Bitcoin Core.

General bitcoin questions and/or support requests are best directed to the Bitcoin StackExchange at https://bitcoin.stackexchange.com.

For reporting security issues, please read instructions at https://bitcoincore.org/en/contact/.

If the node is "stuck" during sync or giving "block checksum mismatch" errors, please ensure your hardware is stable by running memtest and observe CPU temperature with a load-test tool such as linpack before creating an issue! -->

<!-- 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. -->

aboutAction->setEnabled(false);
    aboutQtAction = new QAction(platformStyle->TextColorIcon(":/icons/about_qt"), tr("About &Qt"), this);
    aboutQtAction->setStatusTip(tr("Show information about Qt"));
    aboutQtAction->setMenuRole(QAction::AboutQtRole);
    optionsAction = new QAction(platformStyle->TextColorIcon(":/icons/options"), tr("&Options..."), this);
    optionsAction->setStatusTip(tr("Modify configuration options for %1").arg(tr(PACKAGE_NAME)));
    optionsAction->setMenuRole(QAction::PreferencesRole);
    optionsAction->setEnabled(false);
    toggleHideAction = new QAction(platformStyle->TextColorIcon(":/icons/about"), tr("&Show / Hide"), this);
    toggleHideAction->setStatusTip(tr("Show or hide the main Window"));
    encryptWalletAction = new QAction(platformStyle->TextColorIcon(":/icons/lock_closed"), tr("&Encrypt Wallet..."), this);
    encryptWalletAction->setStatusTip(tr("Encrypt the private keys that belong to your wallet"));
    encryptWalletAction->setCheckable(true);
    backupWalletAction = new QAction(platformStyle->TextColorIcon(":/icons/filesave"), tr("&Backup Wallet..."), this);
    backupWalletAction->setStatusTip(tr("Backup wallet to another location"));
    changePassphraseAction = new QAction(platformStyle->TextColorIcon(":/icons/key"), tr("&Change Passphrase..."), this);
    changePassphraseAction->setStatusTip(tr("Change the passphrase used for wallet encryption"));
    signMessageAction = new QAction(platformStyle->TextColorIcon(":/icons/edit"), tr("Sign &message..."), this);
    signMessageAction->setStatusTip(tr("Sign messages with your Bitcoin addresses to prove you own them"));
    verifyMessageAction = new QAction(platformStyle->TextColorIcon(":/icons/verify"), tr("&Verify message..."), this);
    verifyMessageAction->setStatusTip(tr("Verify messages to ensure they were signed with specified Bitcoin addresses"));
    openRPCConsoleAction = new QAction(platformStyle->TextColorIcon(":/icons/debugwindow"), tr("&Debug window"), this);
    openRPCConsoleAction->setStatusTip(tr("Open debugging and diagnostic console"));
    
    openRPCConsoleAction->setEnabled(false);
    usedSendingAddressesAction = new QAction(platformStyle->TextColorIcon(":/icons/address-book"), tr("&Sending addresses..."), this);
    usedSendingAddressesAction->setStatusTip(tr("Show the list of used sending addresses and labels"));
    usedReceivingAddressesAction = new QAction(platformStyle->TextColorIcon(":/icons/address-book"), tr("&Receiving addresses..."), this);
    usedReceivingAddressesAction->setStatusTip(tr("Show the list of used receiving addresses and labels"));
    openAction = new QAction(platformStyle->TextColorIcon(":/icons/open"), tr("Open &URI..."), this);