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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)? -->

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<!-- 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. -->

#include <qt/guiutil.h>
#include <qt/modaloverlay.h>
#include <qt/networkstyle.h>
#include <qt/notificator.h>
#include <qt/openuridialog.h>
#include <qt/optionsdialog.h>
#include <qt/optionsmodel.h>
#include <qt/platformstyle.h>
#include <qt/rpcconsole.h>
#include <qt/utilitydialog.h>
#ifdef ENABLE_WALLET
#include <qt/walletframe.h>
#include <qt/walletmodel.h>
#include <qt/walletview.h>
#endif 
#ifdef Q_OS_MAC
#include <qt/macdockiconhandler.h>
#endif
#include <chainparams.h>
#include <init.h>
#include <interfaces/handler.h>
#include <interfaces/node.h>
#include <ui_interface.h>
#include <util.h>
#include <iostream>
#include <QAction>
#include <QApplication>
#include <QComboBox>
#include <QDateTime>
#include <QDesktopWidget>