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.
{
    if (nProgress == 0)
    {
        progressDialog = new QProgressDialog(title, "", 0, 100);
        progressDialog->setWindowModality(Qt::ApplicationModal);
        progressDialog->setMinimumDuration(0);
        progressDialog->setCancelButton(0);
        progressDialog->setAutoClose(false);
        progressDialog->setValue(0);
    }
    else if (nProgress == 100)
    {
        if (progressDialog)
        {
            progressDialog->close();
            progressDialog->deleteLater();
        }
    }
    else if (progressDialog)
        progressDialog->setValue(nProgress);
}
void BitcoinGUI::setTrayIconVisible(bool fHideTrayIcon)