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.
const QString &filter,
    QString *selectedSuffixOut)
{
    QString selectedFilter;
    QString myDir;
    if(dir.isEmpty()) 
    {
        myDir = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
    }
    else
    {
        myDir = dir;
    }
    
    QString result = QDir::toNativeSeparators(QFileDialog::getOpenFileName(parent, caption, myDir, filter, &selectedFilter));
    if(selectedSuffixOut)
    {
        
        QRegExp filter_re(".* \\(\\*\\.(.*)[ \\)]");
        QString selectedSuffix;
        if(filter_re.exactMatch(selectedFilter))
        {
            selectedSuffix = filter_re.cap(1);
        }
        *selectedSuffixOut = selectedSuffix;
    }
    return result;
}
Qt::ConnectionType blockingGUIThreadConnection()