Noticed this while reviewing #13529, but it's also in master @ 5ba77df. On macOS 10.13.6:

<img width="209" alt="schermafbeelding 2018-08-01 om 16 22 09" src="https://user-images.githubusercontent.com/10217/43527498-0f571db4-95a7-11e8-8d90-7863947a7689.png">


<img width="178" alt="schermafbeelding 2018-08-01 om 16 12 51" src="https://user-images.githubusercontent.com/10217/43526994-c9a515ec-95a5-11e8-96b8-9e2513e9aac5.png">

* `Show` in the action menu doesn't work if the app was hidden by `Command + H`, it does work when hidden through this menu
* send and receive don't unhide the window when opened for the action menu. It does navigate to the right tab. The other actions do work (sign, verify & debug window)

Clicking "Toon" (= macOS native show) does work, suggesting the GUI uses some non-native method of hiding.
#include <shlobj.h>
#include <shlwapi.h>
#endif
#include <QAbstractItemView>
#include <QApplication>
#include <QClipboard>
#include <QDateTime>
#include <QDesktopServices>
#include <QDesktopWidget>
#include <QDoubleValidator>
#include <QFileDialog>
#include <QFont>
#include <QKeyEvent>
#include <QLineEdit>
#include <QSettings>
#include <QTextDocument> 
#include <QThread>
#include <QUrlQuery>
#include <QMouseEvent>
#if QT_VERSION >= 0x50200
#include <QFontDatabase>
#endif
#if defined(Q_OS_MAC)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#include <objc/objc-runtime.h>
#include <CoreServices/CoreServices.h>
#endif
namespace GUIUtil {
QString dateTimeStr(const QDateTime &date)