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.
QString *selectedSuffixOut);
    /** Get open filename, convenience wrapper for QFileDialog::getOpenFileName.
      @param[in] parent  Parent window (or 0)
      @param[in] caption Window caption (or empty, for default)
      @param[in] dir     Starting directory (or empty, to default to documents directory)
      @param[in] filter  Filter specification such as "Comma Separated Files (*.csv)"
      @param[out] selectedSuffixOut  Pointer to return the suffix (file type) that was selected (or 0).
                  Can be useful when choosing the save file format based on suffix.
     */
    QString getOpenFileName(QWidget *parent, const QString &caption, const QString &dir,
        const QString &filter,
        QString *selectedSuffixOut);
    /** Get connection type to call object slot in GUI thread with invokeMethod. The call will be blocking.
       @returns If called from the GUI thread, return a Qt::DirectConnection.
                If called from another thread, return a Qt::BlockingQueuedConnection.
    */
    Qt::ConnectionType blockingGUIThreadConnection();
    
    bool isObscured(QWidget *w);
    
    void bringToFront(QWidget* w);
    
    void openDebugLogfile();
    
    bool openBitcoinConf();
    /** Qt event filter that intercepts ToolTipChange events, and replaces the tooltip with a rich text
      representation if needed. This assures that Qt can word-wrap long tooltip messages.
      Tooltips longer than the provided size threshold (in characters) are wrapped.
     */
    class ToolTipToRichTextFilter : public QObject