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 (!clientModel || !clientModel->getOptionsModel())
        return;
    OptionsDialog dlg(this, enableWallet);
    dlg.setCurrentTab(tab);
    dlg.setModel(clientModel->getOptionsModel());
    dlg.exec();
}
void BitcoinGUI::setNumBlocks(int count, const QDateTime& blockDate, double nVerificationProgress, bool header)
{
    if (modalOverlay)
    {
        if (header)
            modalOverlay->setKnownBestHeight(count, blockDate);
        else
            modalOverlay->tipUpdate(count, blockDate, nVerificationProgress);
    }
    if (!clientModel)
        return;
    
    statusBar()->clearMessage();
    
    enum BlockSource blockSource = clientModel->getBlockSource();