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(!uri.isValid() || uri.scheme() != QString("bitcoin"))
        return false;
    SendCoinsRecipient rv;
    rv.address = uri.path();
    
    if (rv.address.endsWith("/")) {
        rv.address.truncate(rv.address.length() - 1);
    }
    rv.amount = 0;
    QUrlQuery uriQuery(uri);
    QList<QPair<QString, QString> > items = uriQuery.queryItems();
    for (QList<QPair<QString, QString> >::iterator i = items.begin(); i != items.end(); i++)
    {
        bool fShouldReturnFalse = false;
        if (i->first.startsWith("req-"))
        {
            i->first.remove(0, 4);
            fShouldReturnFalse = true;
        }
        if (i->first == "label")